What do I do?

My daughter who is now 20 years who we will call H suffers from a Mental Illness, not clinically diagnosed as yet. She has an older sister who is 24.
We have only just been going to see a Phychiatrist in the last 4 months. After going to through the local council & neutophcologist for advice.
Here's our story:
When she was 4 she was diagnosed with a mild intellectual disability. Schooled at a specialist school till she was 16. Lost some close family friends on the way as they were reaching high school years as they thought H was "different" & wasn't "trendy" enough for them. She was basically embarrassing. She was always on the outer as she could not express herself properly & was a little slower.
When H was 15 we moved away from an area in which we lived for 20 years for a change. Things were looking good, we found a specialist school nearby to accommodate H but only to be told that she didn't need to be in a specialist school as Mainsteam would've been good with an assistance of an aide. So we transferred her to mainstream. She went down a Year level to give her more of a fair go in learning. The school & children were very kind, they were understanding & she made many friends but within 4 months things were worsening. She would come home saying she was being bullied & having arguments with most of the girls in the group. The teachers intervened & found a new group for H to associate with. As time went by H become more recluse, she would only have 2 friends. Her problem was that she still had her best friends from her old school but she felt as though she didn't want to get close to anyone from her new school so she wouldn't loose her friends from her old school. Eventually she lost her friendship with the girls from her old school & was left with one friend from the new school but most of the time she would be in a group of girls at school but they wouldn't talk to her. This broke my heart.
She still did well In school as she was determined to prove to everyone that she was smart & can do this. She was thriving through Year 9, 10 & then Year 11. Mind you this is a child that attended a special school all her life. So we were proud & so was she as she thought she would never get this far. She loved school.
Going back a bit now:
After 6 months of moving to the new area, her sister moved out back to the old area & this upset H. She then had no one, only me. I left work so that I can be there for her as a friend & a mother. She was visiting her sister on weekends. It's sad cause we have been here for nearly 5 years & the relationship with her sister has also deteriorated as you need to have patience to speak to H as she goes on about things (it's hard to explain). So H has completed Year 12 with a Cert ii in Hospitality. We are so very proud of her.
Now it's the 1st year since she's left school staying at home with no motivation in finding a job, so she is doing a 20 week beauty Course, which I am doing with her to act as her aide as well as studying myself.
I was hoping that her attitude would change & this would motivate her to do things or meet new people. No she still doesn't go out. She's met a friend on the internet & has been seeing him for 4 months. In this time if they're together & happy she's happy (but still at home & lazes around) but when they are not together, well she threatens to harm herself & myself They constantly fight but currently have broken up & this is why I am on this page. This & previous boyfriends she does the same thing. Calls them until they block her from calling & then she puts her phone on private & continues to contact them. She is very obsessed when it comes to boyfriends. We had just sought a Phychiatrist (last 4 months).after trying hypnosysis as we thought it was depression or we were just in denial. In previous scenarios I was able to control the situation but a few weeks ago H was getting violent & I decided to call the police. This was only done as a scare tactic for her, which has worked slightly. H is aware that if the police are called again, she will have no choice but to be taken away to a safe place. So when she gets really upset I just remind her of this & she backs off.
So at the moment she is up till all hours of the night till morning (as now 2.50am) hence why I am up. This is on most nights regardless if in a happy or sad mood. I need to know if there is anyone or any facilities out there like a renabilitation Centre who can help H with her issues.
These issues usually occur at night but the Phychiatrist is not available after hours & I don't want to call the police & I have contacted an after hours emergency assistance help line & they told my husband & I to just let her get her way. That was the most ridiculous advice I have ever heard. That is n a situation like this of if we feel she's getting into that situation we should let her win.
She is a very unstable young lady & I try so hard to be there for her but I am getting drained as this has been happening for nearly 5 years but worsening over the last 8-12 months.
It frustrates me that I still am family friends with the parents of the girls who dumped Hannah as they're lovely but their children are nasty & I am a god mother to one of them. Otherwise I would've cut ties with them a long time ago, or should I (advice needed) it doesn't bother H that we still keep in touch with the parents but H just doesn't have anything to do with their children & as they're older now & drive we don't see them when we go visiting as much.
Am I doing the right thing? Or is there somewhere I can go or is there more I can do?
Needing urgent advice please