Well SL doesn't seem to be doing to badly for himself. He's going to make enough money to live a nice life, surely. He's stable, highly educated, ambitious, drug free, and gave LB a dog which requires stability and responsibility...that's the sort of lifestyle he sees for himself. SL is on the high road.
With DM IMO it was all bout the fast lifestyle. LB had a pretty impossible dream to become an actress and this I think sucked her into the lifestyle of schmoozing at bars, and drugs.
Once you add drugs into the equation I think your good judgement can become...uh, somewhat relaxed? Reduced? Being a high end escort probably wasn't much different than LB's general fast lifestyle with DM and his entourage except that she got paid....in part with more drugs to reinforce the cycle.
DM gave LB drugs and used LB for sex and then she fought over him with her best friends.
LB became depressed and despondent and uninterested in doing anything to help herself and when she did react she lashed out. Was she really crazy or was she having a totally sane reaction to the lifestyle she was living and the people around her?
If she cut her two "friends" and DM out of the picture and gave up on the actress dream and stayed away from the drugs and alcohol, wouldn't a certain amount of sanity have returned?
The problem IMO was that she was going to the doctor and they were giving her even more mind-altering drugs to go with her street drugs and doing nothing to suggest that her lifestyle was hurting her.
A doctor should have suggested to her that she was living a faster lifestyle than she could handle and referred her to rehab, IMO.