She might have been at a low point, but I don't think she was going to suicide just for the sake of it. Perhaps feeling down made the choice to sacrifice herself easier, but it's still a sacrifice nonetheless.
Just for the sake of it, another way of interpreting all this, is Sasha realizing that Anne doesn't need her, and that she's well off as-is. Sasha might have been overly controlling with Anne because she thought she needed to be, since Anne can be a little naive. She might have thought she was doing her a favor by making her do these things she was trying to get her to do. Perhaps when she realized Anne didn't need all of that, she could literally and figuratively let go.
I wouldn't be surprised if we find out that Sasha has abandonment issues. If her parents weren't around much, or at all, then that would explain her independence, general disregard, or even disdain, for authority, and her controlling nature. She might be so controlling towards Anne because she doesn't want to lose her. So when she sees Anne with her new family, it hits especially hard for her, and perhaps she's sad for herself, but happy that Anne has what she didn't.
Or maybe all of the above.