How about you call her cell phone provider and pay the bill directly via a credit card?
If it's a national provider like Verizon, you could most likely go to the office, give them her number,
and pay the balance in cash as well I would think.
Bus pass could be handled through the social worker perhaps or a church as was suggested. I don't know if a bus pass would have much resale value "on the street", especially a monthly one.
I see your point about giving her even a small sum of money if she possibly planning another suicide attempt. Even a hundred dollars might buy enough drugs etc. to OD
if that was in her mind.
I'm sorry you are dealing with this. I hope she is serious about getting better.