From what you describe, I would imagine that she's the author of all the drama in her life. And frankly, her behaviour would drive away the best of us.
My advice is to draw a line in the sand as to what behaviour is acceptable to you.
Clinginess: tell her that you have a life outside of her and will text her when you can. Tell her that you will not tolerate her getting upset or angry if you're not available to respond to her.
Social Media: tell her that you like social media and will use it as you see fit. If she doesn't like it, then she needs to either suck it up or leave...but you will not be entering into any discussion on that topic with her.
Paranoia: refuse to discuss it. Tell her that you will simply not engage if she's being paranoid
Thing is, each time you apologise/explain/give in to her control and neurosis, you're rewarding her behaviour. Tell her that you love her, but you cannot and will not tolerate all this crap she's putting on you. Time to stand up for yourself
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.