I get you. I really do.
Even with all the crap, I'd choose my life over most of my friends'. Sure, I get envious about the ease with which they can book babysitters, have a casual pub lunch, have a lazy holiday with brunches and lazing around the pool, etc. But they don't have my dd. And I'd rather have my family, than be easily able to do all that (even though, at any given moment, I may really, really want to do that)
Choosing something different doesn't mean that your dd thinks your life is shit. It means she wants something different.
I can't think of anything worse than being a dentist, but lots of people choose that (and enjoy it!) for their careers.
Even without disability, I'd have chosen to be at home more with my children rather than having a high flying all hours career. That doesn't mean I think all career parents have shit lives, or make shit choices - just means that choice wasn't for me (just as well, since I wouldn't have been able to do it anyway, as it turns out!).
My best friend is childless by choice. I don't understand her point of view, but she's happy. I'm sure she thinks part of my life is shit, but she also knows how much I enjoy my children.
Have you discussed this with your dd? Tried to find out why she feels that way? (I don't mean you should sit her down and quiz her about it, but gather thoughts and views while idly chatting, over a period of time)
It could be that she is scared she wouldn't manage.
It could've that she doesn't want children at all.
It could be (as a pp said) that she's just currently hates siblings, because, you know, she just does
It could be her trying to see what you'd think if she didn't want children.
It could be that she said the worst thing she could during an argument, because she knew it would hurt as you are (naturally) protective of ds.
It could be that she was trying to find a way of opening a discussion about whether you think people can work and have children (I could be wrong, but I seem to think you are a sahm?), and even do so when there are disabilities.
She might just be having a teenage angst 'I hate my life' interlude, and she'll get over it.
I don't think here's any reason to think that these views will be her final choice re: having children. She's 13. So many things change once partners arrive on the scene, and love, and biological clocks etc. She's at the very beginning of working out what she may want as an adult.