"Killa Kevin" is the ultimate manipulator. He drugged her when she was undergoing detox in the hospital. He kept her drugged and as you probably noticed she was getting worse and worse in the last year of her life. And HKS is the one that masterminded that whole scenario you described. She was under the thumb of him and under the influence of drugs given to her by him. She was an addict. She was paranoid because HKS had her convinced that Birkhead was going to take the baby away from her because of her addiction.
But Birkhead tells us that she wanted him to marry her. Remember, she told him to pick out a ring from Tiffany's. And altho he may have wanted to marry her, he says that he didn't want to do it just cuz she was pregnant. What i read between the lines there is that he didn't want to do it because he had reservations about her ability to overcome the drug addiction. He was probably waiting to see if she would try to go clean.
Which brings me to my theory about her possibly going to FLA to be detoxed and/or for rehab. Yes, i know about the boat, but that is a HKS setup (premeditated). HKS may have known she went for rehab and the boat deal was his idea for covering that up. HKS wouldn't have wanted the rehab. Because if she went clean, she would be in her right mind and might put two and two together and realize or suspect he had something to do with Daniels death.
I'm sure he was drugging her and she knew it. Even though she's paid the ultimate price for her crimes I'm not going to sugarcoat all the mayhem and mischief she bought into her life. I think it's pretty obvious that when she cut someone out of her life it was for good. She wasn't going back to Birkhead and she would still be fighting today to keep that child away from him if she was alive.
I agree she may have been detoxing in Florida. The deadline was approaching and just in case they couldn't delay the DNA testing..remember they would have had to test Anna too..they wanted to make sure she wasn't drugged up.