Thanks for the update.
I feel for you, and for husband. He shouldn't feel any personal responsibility, she is the one who chose to overdose, she has to take responsibility for it. "The devil made me do it" just doesn't wash. It never has. If she continues to say, "I did it because of you," then she is failing to really look inside at why. Now it is possible that part of the reason why, can at times be medication incompatibilities. But to blame someone else, when they didn't actually force your jaws apart to put the pills in your mouth, then force you to swallow - sorry, not on.
Now, to her choice of older companions - I think you and husband are going to have to find a way to accept this. Her friends drifting off - not a valid reason. There is something more, and it is likely that the "something more" is simply that she is attracted to older males. Or maybe older companions in general.
When I was 13, I had two friends at our church youth group who were going out with guys who were 21. There were a few mildly raised eyebrows but nothing more. The girls' parents accepted the older boyfriends. They were quite nice boys (men) although I felt that the girls were a bit immature. I don't think anything untoward was going on, the boys would have known it was illegal. I was close enough to both girls that I would have known if they had been having sex. I'm certain they weren't.
husband's sister was not really into boys while she was at school, she was too keen on studying. But when she was 16 her parents let her go to the US for a year as an exchange student and of course she didn't feel such a burning need to study - for her, it was a year off. Of course she had to go to school and she did quite well, but was a lot more relaxed and also had much more of a social life, for the first time. And the boys she found she preferred spending time with, were older.
Then she came home and began studying hard again, at college. husband & I involved her in some of our social groups (husband is three years older) and again, although there were boys her own age in our group she was attracted to the older ones, up to ten years older. Her parents were not impressed. husband & I were asked to keep an eye on her, to organise more contact with our own male friends in order to encourage a more age-appropriate relationship for her. Not that she was running wild at all, but she just seemed bored by guys her own age. She even had one young man her age, they had played together as kids, he worshipped the ground she walked on and would have walked over hot coals for her - but she just wasn't interested in him.
She eventually married a guy 15 years her senior. It's been a bit bizarre for me and husband because brother in law is so much older than us, in so many ways. We are fairly young at heart for our age, but brother in law can only be described as a "fuddy duddy". And of course sister in law, after being married to someone so ultra-conservative, has taken on a lot of his outlooks in life. To anyone meeting us, she would seem the elder.
The thing is - she always had a strong preference for older guys. And there can be many reasons for this, not necessarily one of "I am looking for a father figure" or "I am looking for someone who is far more experienced, someone who prefers younger girls." In sister in law's case I think she was simply a very intelligent young woman who was looking for someone who could be her intellectual match, and most guys her age were too immature for her.
It could be the same for your daughter. Simply by disapproving, I don't think you and husband are achieving anything in terms of giving her a better direction or encouraging her to choose more age-appropriate partners. In fact, you could be making these older guys more attractive in her eyes, "forbidden fruit". And while there may be a couple of these guys who could be attracted to the "jail bait", it's also quite likely that they too are enjoying stimulating conversation with her. Especially if she refers to them as friends, it indicates that companionship is high on her list of priorities.
She's only a few months away from 17 years old, pretty much the same age sister in law was when she first began to get interested in guys. And in her case, her preferences for older, more mature guys never changed despite everything her parents tried. In fact, if they hadn't tried so hard I suspect she would not have married brother in law (who frankly I tihnk was a bad choice for her, but not because of his age; I have other reasons for disliking him).
So perhaps an alternative option for you and husband could be to welcome her choices for now, invite them home so you can meet them and get to know them well. If they are so much older than her, they may find they enjoy your company more than hers! And THAT would do more to make your point to her, than anything else!
But even if it does nothing to curb the mutual attraction, simply by inviting them home and encouraging the guys of her choice to spend time in your presence, you've got her where you can see her and you're chaperoning.
It also removes one reason for her to be giving husband a hard time - she won't be able to complain that he is interfering in her relationships.
In the meantime - keep doling out those pills carefully. Very sensible.
Marg