Just wanted to say that I've read your update, and it sounds like you're doing all the right things. Services will always try to avoid admission when possible, but it is there as a last resort option. I'm glad your daughter is opening up a little, that's a good thing. She may feel rather relieved that you know - when I am very depressed I don't want to worry my mum and so try to keep it hidden, but when she does know it can be a bit of a relief to be able to drop the act etc.
I think if your daughter can stay in school then that is definitely something to be encouraged. When I mentioned her having time off I was thinking of a few days if she needed it, not leaving school. As long as she feels able to go into school then encourage it - it is only if she is really struggling to cope with it that it's a problem. I was 17 when I was first diagnosed with depression, and for the first year or so I did find it helpful to have that routine and structure etc - it was only when I became more unwell and wasn't able to do any work because I just couldn't focus my head, and had to leave classes because I was finding it too overwhelming and stressful that it became a negative thing for me, but at that point I was feeling very suicidal (for a few months I guess) and I did end up trying to kill myself, so it makes sense that I couldn't cope with college, particularly as it was exam season.
How to talk to someone suicidal is a tricky one. I think the most important thing is to listen, really listen, and just let her know that you are there for her. You may not have the answers, and that's ok, and it's ok for her to know that too. Try not to judge what she is saying, and don't argue about it. Just listen, support, ask her what she thinks might help, make suggestions if you have any, but don't force the issue, don't be patronising, don't tell her she is being selfish (people often seem to think that it's helpful to say that - it really isn't, you have enough guilty feelings when you're feeling depressed anyway, someone telling you that you're being selfish doesn't help), if you can relate to anything she is saying in any way then use that, but really the most important thing is to listen and be supportive and non judgemental.
If you feel like things are getting worse then please either contact CAMHS or take her to A&E. Hopefully she will be ok until her psychologist is back, but don't be afraid to get her seen by someone else in the meantime if you need to. She may not want to talk to anyone else, but they do know how to assess people who don't want to talk etc, and if her safety is in doubt then she does need to be assessed. But if you feel like things are fairly stable, and you're able to keep an eye on her at home then obviously that is preferable to getting her to speak to someone she doesn't want to.
Keep posting if it helps. I do think you are doing the right things.