15yo daughter keeps running away

TW SELF HARM**MENTAL HEALTH**SEXUAL ASSAULT

So my daughter who’s 15 keeps running away from home. Honestly I don’t even know where to start. Her bio dad moved interstate in 2013 and basically forgot she existed. She visited a few times where his (now) ex gf made comments towards her like ‘I don’t like you’ ‘why are you laughing at what I said, it’s not like we’re friends’ which I didn’t know about until recently. She use to call me crying asking to come home which broke my heart but there was nothing I could do. Eventually things got so bad and I told him without the correct orders in place, I would no longer be sending her. He never tried amend them or have new orders placed so I left it alone and she has been with me full time ever since. My husband and I have been together 12 years and married for 6 which has been her dad since the beginning. She’s called him dad from pretty much the get go. We have a son together who is 9 and is adhd so requires a little more of my attention at times however, I do try and split things evenly. In fact, my daughter and I are quite close and considered best friends as she puts it. Her bio dad step father also sexually assaulted her and drugged her with his bipolar meds when she was 5-6 which she had no memory of until she was 12 to which I put her into counselling. Over the last 12 months she started running away. It started where she’d go for a day and come back where I’d blow her phone up and track her down and bring her home. She’d lose her phone, we’d talk about it and she’d be grounded for a week or 2. Then things got worse. She started leaving for around a week last month and this time she blocked my number, blocked me on all socials and I have no idea where she is. She’s also just changed schools and claims the reason she ran away the first time was because she didn’t know anyone and became anxious. We sorted it out when she came home and she went back to school for 3 days and then left again last Saturday. That’s when she blocked me. I don’t know what else to do. I’m at my wits end with her and nothing I say or do is keeping her from this path of destruction. She use to self harm which stopped when she started running away. That’s her new form of self harm. I got a call from a sector of child safety that offers help to families. The school sent the request and I have a phone appt with one of the counsellors in a week so hopefully she can help us. I just can’t deal anymore. I’m going out of my mind worrying about where she is and complete frustration because she doesn’t get this is so destructive and is going to end up ruining her life!