I don't see this mom in quite the bad light most do, maybe because I'm a mom. Just sounds like a very worried mom whose separated many miles from a daughter she's concerned about.

Her intentions are good. She's trying to actually be sure doing this isn't a burden financially to you, but at the same time she's interfering a bit too much and probably not realizing it.

Just reassure the mom you've got it covered. Thank her for her thoughtfulness and willingness to help out but that it isn't necessary.

Mom's just worried and grateful there is someone there for her when she can't be herself. You can set boundaries by simply reassuring her that you are her daughter's friend and perhaps just encouraging her to talk directly to her daughter rather than to you. Perhaps suggest that that kind of direct communication is really what would most help her daughter.

I suspect once the daughter gets past this crisis and seems to be doing better, the mother will stop contacting.