'AITA for getting mad at my stepsister for revealing her pregnancy during my engagement party even though she "didn't mean to"?'

I have a stepsister "Taylor" who is 2 years older than me. We were 12 and 14 when our parents married, and Taylor hated my mom and I from day 1. She can be a mean girl, and she definitely thinks she is better than everyone. She was also jealous and possessive of her dad. I wasn't thrilled about the new blended family, but I wanted my mom to be happy. Taylor was nothing but rude to my mom.

Growing up I always felt like I was in her shadow. I recently got engaged and my mom and stepdad threw me a beautiful engagement party. Taylor was there with her husband, and a couple people were making jokes about how she will probably try to wear white to the wedding.

My stepdad made a joke about how he doesn't care if she is his daughter, he is going to pay multiple people to be there with red paint water balloons, because Taylor doesnt get to get away with her sh!t at the wedding.

Suddenly Taylor began crying which is so out of character that everyone was shocked. She said she was just pissed at her dad for picking me over her, but her husband was trying so hard not to smile. Taylor told us all to shut up and not look at her because she can't help it. My stepdad was trying to explain that she needs to learn a lesson, but he still loves her.

Taylor finally blurted out that it isn't that serious, but she is pregnant and she just has been crying about everything. I was in shock that she would say that. Her grandmother heard and made a big deal of it to everyone, so by the end of the night, everyone had congratulated her. My mom was telling my stepdad how awful Taylor was for doing that and he said she didn't mean to.

I replied that no one interrogated her, so she is still accountable for her actions. Taylor's husband was a bit tipsy at this point (doing celebratory shots like this party was to celebrate his baby) and called us @$$holes and jealous.

I said that she has no manners because deep down she is an insecure little girl. Her husband was pissed. My mom told my stepdad that we don't want her at any more of my events and he got upset and felt we were too hard on her. Now people are calling me jealous and a bridezilla.

EDIT: the people teasing her in the beginning were closer to her than me, and that group always teases each other. She is very proud of her flaws, and her husband has openly said he likes bitchy and difficult, and thinks it is cute. I do think what her dad said hurt her, but she was not being bullied

What do you think? AITA? This is what top commenters had to say:

[deleted] said:

NTA. Taylor knew exactly what she was doing turning on the waterworks. Which is why your stepdad's promise to handle her at the wedding means nothing: he can't tell when he's being played. Leave her and her drama out of it (as best you can, anyway;

I wouldn't be surprised if she tries to arrange some kind of counter-programming or "emergency" day of, in which case you may just need to accept the possibility your stepdad won't be there, either).

Never_Toujours said:

Info: to clarify: guests were mocking her right in earshot for seeking attention before she sought attention by revealing that she is pregnant?

OP responded:

The people mocking her were closer to her than me. Even her husband made a joke about her wearing white. Taylor is the type of person who says she is proud of her bitchiness, and her husband seems to like it, so they were mocking her, but not even in a mean way. She is very sarcastic with people she likes, so that was a normal conversation for them

No-Satisfaction-1878 said:

NTA, but don't invite her to the wedding, I'm sure she's going to ruin it.

jobrummy said:

This sounds like an awful situation. Her father joined in with other people to pick on her about a made up scenario, made her cry, and instead of just dropping the subject, especially after basically being told to leave her alone, they just… kept doing it?

What lesson is being taught here? I really want to say the @$$hole here is your stepfather because this lifelong insecurity about having lost her father’s affection has to come from somewhere.