Because the people on Game of Thrones are not real and are actually played by a special subset of superior humanity called "actors" and "actresses," the impression the show may have given you of Septa Unella is not actually reflected in her daily life.

The smallfolk are dirty, so very dirty.
The smallfolk are dirty, so very dirty.

Unlike the dour Septa Unella, all actresses are gorgeous, with pretty much no exceptions. That's a great example of sexism, since John C. Reilly is a famous actor and he looks like a mountain goat. But the point here is that Septa Unella is a beautiful woman when going by her human name, Hannah Waddingham.

Sources: h/t Uproxx