I'm sorry, but that's awful. Why today? Please at least tell her to drop it off at a vets, and they can rehome it. NO vet should put a healthy dog to sleep, and your friend deserves a slap for having one in the first place, and then doing this so callously.
Shocking.
Edited to add;I'll take it, rather than PTS, and I'll find a damn good home for it, so on no acount have it PTS! I don't even know where she is, but please don't let this happen!