'My step-sister is marrying my cheating ex and I'm refusing to be her bridesmaid, AITA?' UPDATED

"My (25f) stepsister ss (23f) is getting married to my ex(26m)"

We were as close as any two sisters growing up. My mum and her dad met when we were 8&6 and we got along really well from the get-go. My exbf and I broke up 2 years ago, he cheated on me and I found out about it a week after he proposed to me. 5-6 months later ss told me that she and exbf have started dating. I couldn’t believe my ears.

I was very angry at her but the rest of the family (mum, stepdad, two half sisters) didn’t think it was a betrayal at all and my mom once yelled at me to grow up and move on. I gradually distanced myself from my stepsister, without making a fuss. I just poured myself into my studies instead and hid behind the “I’m swamped” excuse.

I started dating my current boyfriend cb (25m) about 10 months ago. The only problem is that ss used to have a huge crush on him, and she still, to this day, text and dm him. They never dated. I haven’t told anyone in my family that I’m seeing someone.

ss and exbf got engaged and they have sent the wedding invitations last month(wedding in june). I didn’t rsvp because I don’t want to attend. last week my mum asked me to visit. When I got there mum was waiting with ss, her bff (and MOH), my half sisters and exbf’s sister. It was an “intervention”. my mum started by saying that I needed to stop alienating myself from everybody and get over the hurt.

Ss is getting married and she wanted me as a bridesmaid. I told them NO! Ss started crying saying I’m ruining her wedding. She asked if it has to do with me not having a +1 because she could pair me with one of exbfs single best men and I wouldn’t feel lonely then.

I got really angry and told her I didn’t want to go to HER wedding because I don’t like her. She started crying again calling me bitter and a hag for purposefully wanting to hurt her on her big day. I left.

My mum called me later saying if I didn’t show up at least as a guest, I’m cut off the whole family. You see they need me there so people see there’s no hard feelings between us and that I have blessed their marriage because she has been getting a whole lot of sh*t from the family for what she did to me.

I’m so angry now. What’s between ss and I is broken beyond repair. Why is it so hard for them to understand. Plus I DO have a plus one should I decide to turn up. And ss would regret the day she invited me then. I have a half mind to do it and ruin her day. I love my mum and my sisters but I’m tired of them choosing ee’s side.

And I know mum is serious that she would cut me off if I didn’t attend. She loves my stepdad very much and upsetting ss means upsetting him. Any advice on how to tackle this? Because however I turned it I am the loser.

What do you think she should do?

UPDATE:

Hi again!

Ss=step sister Cbf=current boyfriend Exbf=ex boyfriend

Before I update I want to thank you very very very much. When I wrote here I was so hurt and consumed with anger that I was planning a very cheap revenge on my ss. But since then and with the amazing advice I got from you I realized that pettiness isn’t the answer. I thought back and came to the conclusion that the only hurt I was feeling was because of my mum.

Since my exbf cheated I have felt that my mum let me down by not supporting me. I don’t care about ss or exbf. I’m very happy with my life now and I love cb. I decided to try one last time to fix things with mum and explain to her how hurt I have been by her treatment. I also decided to tell her the truth.

On Friday I visited mum, she was alone at the house. I started by telling her that I was hurt about the “intervention” because I didn’t think I needed one. That I was hurt that she always took ss’s side, to please my stepdad, and that I have many reasons for not attending ss wedding.

While I don’t feel hurt anymore about her (ss) betrayal, our relationship has changed and I don’t see her as my sister anymore. I don’t feel obligated either to try and repair her reputation by going to her wedding. She made a very controversial life choice and even if I’m not hurt by it anymore she must’ve known people will be giving her a hard time and that I honestly don’t understand why she cared.

And lastly, I told her about cbf. I told her about ss probably still has feelings for him and it wouldn’t be nice for us to go to her wedding and ruin her day. I told her I wasn’t ready to make our relationship official yet and that if ss knew he would be my plus one she would change her mind about inviting me.

I saw that my mum was getting more and more upset the more I talked. When it came to the subject of cbf she was shaking with suppressed rage. After I finished she told me she was right in thinking that I’m a vindictive hag that she’s ashamed of me and that my bitterness is the reason I will end up alone.

She told me I was pathetic for hooking up with ss’s old love and she forbade me from telling anyone about him. “And you should break up with him if you know what’s good for you” she threatened to tell cbf that I’m using him to get back at ss and then she kicked me out of her house.

Yesterday, when I was in the kitchen I heard the doorbell. Cbs opened and it was ss with exbf. When she saw cbs she asked what are YOU doing here. I came out of the kitchen and she was terrified and her eyes full with tears. Her plan was to sit and talk, me her and exbf to sort things out but when she understood what’s going on she started crying.

She called me names, cursed me and threw the shoehorn I have in the entrance at me. She kept yelling HOW COULD YOU DO THIS TO ME. Cbf asked them to leave and blocked her from getting at me. She left in tears, exbf confused after her.

Mum sent me a long email today telling me that she was disgusted by my actions (she thought I planned for ss to find out about cbf and me). She forbade me from ever contacting her or my sisters and told me that if I don’t end things with cbf immediately she will make breaking us up her priority. I showed cbf the email.

He is very distraught. He asked me if I would consider moving to another city with him when I finish school and we move in together. We’ll see what happens but I like his suggestion. It was the first time he talked about moving in together. I would’ve been over the moon if I wasn’t so heartbroken.

Here is what some top commenters had to say:

[deleted] said:

"She told me I was pathetic for hooking up with ss’s old love..." But the stepsister hooking up with OP's ex is fine? Mum is actually more batshit crazy than the stepsister. I really hope OP makes a break for it, because she'd be a whole lot better with that collective group of assholes in her rear-view.

Bryanormike said:

Keep the email as it will be important if she ever tries to apologize to you and if you ever want to remind yourself why you two are not talking. I don't mean it in a vindictive way but as a reminder of the choices your mother made along with step sisters choices.

Again, not to be vindictive or petty. But if she ever comes and doesn't know what to apologize for you can literally just send the email back to her . Good job showing him the email so he's aware. Good luck, there isn't anything to do anymore but just focus on yourself.

ShyGamerMama said:

So she can date your ex and that’s okay lol. You don’t need them, honestly. Blood means nothing. Surround yourself with people that actually support you and love you. Your mother is absolutely shameful.

Belf17 said:

DNA doesn't matter when it comes to toxic people, sometimes you just have to cut them off to realize how toxic they were. But I won't lie, i'm happy karma got your stepsister, now your cheating ex is going to marry her while she is still in love with your current BF. They won't last long.

Move to another city, be happy, enjoy life and be ready when you have kids(if you want too) your mom will do a 180 to see the grand kids, don't fall for that she will not change.

Verdict: NTA. NTA. NTA.