Definitely try stopping dragging conversation out of her. My partner doesn't do that but, when I was your daughters age, my mum would and it was just... bad. She'd ask me questions and she'd get one word replies because coming up with a sentence was too much. Then she'd get upset with me because I would start getting really irritated and snappy. It wasn't
her that I was getting irritated and snappy with, it was
me. I wanted to be able to answer her questions properly and talk to her but I just simply couldn't be bothered to put it mildly. It took it out of me to reply with a simple "yes" or "no" nevermind anything else.
Still talk to her. You don't want to stop talking to her! Just don't ask questions that require too much of an answer.. actually, try keeping the questions at a very bare minimum if you can. And don't ask if she's okay! She knows she's not okay and she knows that
you know she's not okay. In that mindset, when I was asked if I was okay all I could think of was "seriously...? You really can't care all that much to not notice that I'm not okay without having to ask..." It's really, really hard for those around "people like me". I don't envy you for one bit but just try and tread easily. Try and think really hard before you say something to her about how someone in her situation might take what you're saying. It could be completely innocent and trying to help but you have to be careful as she's probably hyper alert to any kind of criticism and condescension etc. If it can, in any way shape or form, be taken as being
slightly bad.. don't say it. And things like asking if she's okay. Like I said, she knows that you know she's not okay and by asking, she could feel that you're criticizing her.. "hey, aren't you better by now? Get a grip of yourself!" That's how "are you okay?" sounded in my head when I was bad.
Just.. keep treating her like your daughter. Nothing more, nothing less
edit - do you go out a lot? As a family or just you and your daughter? I don't know if you remember but I told you before that talking therapy never worked for me, what made me feel better was actually getting outside and doing things. Try that. Have a look about where you live for places to go and things to do. It doesn't have to be expensive and it doesn't have to be for long, just get her out of the house regularly. She'll probably resent it, and you, because it's exhausting! But it
will help. The longer I stay in the house, or leaving just to go to school/a friends house then coming home, the worse I felt.
edit again - I know you have other children (do I remember you mentioning a LO?). We have a small city zoo here. It really is tiny; you can walk around it in less than half an hour but it takes longer, and is more enjoyable, when you have a LO and my mum would take me there a lot with my nieces and nephews. Even when I was in an apartment of my own, she'd come round every day and we'd go out and just...
do something.