That part made perfect sense to me. Watching this girl was taking resources away, and if she was determined to kill herself, it was GOING to happen. No one can watch her 24/7, she'd find a free moment. This was just focring the issue, the 'shit or get off the pot' moment. Either she does it, and the group can stop wasting time and manpower, or she realizes she wants to live, and it's over.
Having been in a similar situation, she probably realized that it wasn't going to resolve itself until she really had the opportunity to DO it, and then she'd see whether she REALLY wanted to, or if she wanted to live...
I agree 100%. There've also been suicide moments in the books, both involving characters still around on the show, and I think the show is stealth-addressing those. The two are:
Given the latter, it makes perfect (if cold) sense to let someone off themselves in a relatively controlled manner ... if that's what they're going to do. There's no suicide prevention hotline anymore.