Yikes! Okay, so there are a few issues here.
You say your daughter has OCD, anxiety and depression. Well, OCD is largely about control so, given how excessively restrictive your daughter's life is due to your unreasonable rules, it's hardly surprising she has OCD! Anxiety and depression are also not surprising given the circumstances. I'd be anxious and depressed if I was living like a prisoner in my own home and felt I couldn't breathe for fear of it being wrong.
It is deeply worrying that you talk about your daughter's MH conditions not improving - as though they are bad behaviour that must be corrected. You must realise that until you lighten up and treat your daughter like the adult woman she is, these conditions are unlikely to improve - you are causing the problem then blaming your daughter for it!
You are clearly very focused on your daughter respecting you/your rules. You sound like one of these people who get a kick from insisting upon respect from a younger person regardless of how unreasonable your behaviour is. It's the "respect your elders" thing - that she must respect you just because you are her parents - even if your conduct is unreasonable and not worthy of respect. Try respecting HER... treat her as you wish to be treated. You cannot treat her like a caged animal and expect her to respect the rules that keep her a virtual prisoner.
As for her boyfriend - you admit he himself is a respectful young man so how exactly is he dragging her down? I'm starting to suspect you will never consider any man to be worthy of her. I also suspect the reason you hate his mother is because she told you some home truths and you know that if your daughter is around her boyfriend and his family, she'll get a sense of what it's like to live in the real world and they will encourage her independence. You must understand that if you do not treat her like the intelligent young woman she is and stop treating her like a 5 year old, then you cannot blame her when she seeks respect and happiness elsewhere.
Your daughter is a young woman - and will soon be off to college/university by the sounds of it. How do you intend to continue your obsessive control of her when she selects a college as far away from you as humanly possible? What are your expectations of her when she goes to college?
As someone above asked: how is her boyfriend "dragging her down"? What does her ideal life look like to you? Have you considered that perhaps your own expectations of her and her future might just be a bit unrealistic and unreasonable?
You need to examine your own behaviour - stop blaming your daughter for struggling to live up to your unreasonable demands. It sounds like it is YOU who has to change, not her. Give her respect and the freedom she is entitled to as an adult human being or you will risk losing her forever.