I hate it when people use people for the sole purpose of getting what they want. Especially when B is just an acquaintance to A and A act all nice and close to B. Its really annoying. What's worse is that the B dont know that he/she is being used and just do it cos he/she want to be helpful and friendly. Its not like A cannot get the thing done him/herself!
Tell me, if you're in my shoes and knows what happening. What will you do? I dont wanna hurt either party.