Kathy,
This has been such a difficult time for you and husband...I know difficult child has been putting you through the ringer, and has been talking "smack" about you to whoever would listen. She has landed in this position not from your lack of support, but from her abundance of issues which she hasn't been working on lately. Despite all that, I think your husband made a good call for the following reasons: 1) difficult child jumped at the chance; 2) The place was recommended by a knowledgeable source; 3) It's covered under her insurance; 4) She swallowed a bottle of pills - she is in a bad way. The interventionist thought it was a reasonable choice, too.
It stinks that you have to cover the rent in the meantime, and I get why you're conflicted. It may not even work - she may blow it this time, too. It is a beneficial choice that settled husband's mind, and may work wonders, who knows? It doesn't mitigate the fact that difficult child has been a horse's arse of late, and difficult child may even believe that your future ultimatums, if there are any, would hold no weight because husband caved this time. Who cares? It remains that you and husband will always have a choice about what you will or will not do. Hugs to you and your husband for all your aggravation, worry and financial hardship. I know this is no day at the beach.