Some ideas…

1) “I was actually able to deal with my daughter patiently today because I got support-“

That is wonderful! Anything you can do to keep your cool is worth tons, both for yourself and for success in this challenge. Going for regular walks, alone or with a friend, is very helpful. Walking with someone you can discuss this with — or even someone you wouldn’t discuss this with, is calming on the nerves. Take up some hobby, like sewing or needlepoint or puzzles – something to do when you’re up in the middle of the night and can’t sleep.

2) Whatever you can do to sleep through the night — arrange somehow that you don’t wake up when she leaves (earplugs?) — you need your strength to deal with this. All the extra worrying is unproductive.

3) Whatever you can do to build relationship, confidence, etc., is TOTAL MITZVAH, despite what may seem. Things that for ordinary people are wrong, are right for exceptional cases. I’m not saying halachically, just practically. If an ordinary kid should never be allowed to get away with something, a kid with a fragile mind might be different. Here too, what might ordinarily be a terrible thing – to support someone doing wrong things – in this case might be completely the best possible thing you can do for her, because it will anchor her and one day bring her back.

4) Seek help from professional kiruv people to find out what makes her tick — they’ll know from experience how to get through. Even just to develop a relationship and maintain it, regardless of kiruv itself, it’s important to know practically what she’ll respond positively to. They’ll know.

5) Even on-the-derech children usually (at one stage) do not want to be seen with their parents. All the more so here. So if she might be willing to spend some time with you, it would have to be somewhere she’s in no danger of being seen. If you can communicate to her that you recognize that and respect it, you gain points. Time spent together should be on building a relationship, not a single bit of tension or conflict.

6) Maybe somewhere that her friends would never even go – a Shakespeare playhouse? Choose a comedy (the kind they never study in schools) – I remember seeing Measure per Measure (I think) and it was really funny. Arrange to enter the playhouse at different times, etc., so that no one will see (see point 4) but you’ll sit together. Maybe something like that.

7) Even if she shows no response to your offers of love, deep down she’ll remember them. Show you care not just for her physical health, but also about her feelings. Show respect for what matters to her (not easy!), and she’ll respond to that. Offers of help for things that she feels she needs, may go far. I really don’t know what would work, only one very common denominator comes to mind, which may be ridiculous for a variety of reasons, but “if you’re going out tonight, there’s cash in my pocketbook – take all you need”? Feel free to reject/modify this suggestion!