I THINK I SAW this on Criminal Minds once.
Your recent bolded text changes the original post quite a bit. You said B indirectly lead to A's suicide and now you're saying A killed herself only because of what B did. That's very different.
Anyway, this is easy i think. B was well-intentioned but that doesn't matter at all. B shouldn't have gotten involved and should have supported A and that's it. Nothing beyond that. If B is the parent of A, then that changes everything however. Any other relationship wouldn't excuse B's behavior here though.
1)
Machinations led A to suicide indirectly, but they were indeed the only reason of it. I do not see a contradiction.
2) Wait... what ? How does being a parent "changes everything forever" ? How do a parent has more excuses for driving their child to suicide than other people ? Or more excuses for "getting involved" in their life ? Do you consider an adoptive parent a parent ? Or inactive biological parent ? Do you consider an informal, but major, parental figure a parent ? Do you consider an orphanage's staff parents ? Do you consider...
3)
Both A and B are older than 18. Just to clarify.
4) IMHO, whether A is a parent of B or B is a parent of A or neither is a parent of another one plays exactly no role in the situation. You may consider both (all three, in fact) scenarios, if you wish.