Petty request

I got to know her(A) through my friend (B). B and I were invited to A's place. A liked B so she offered B to have one of her earrings. B also offered me to have one. Her earrings were all hideous and not my style. However, to be polite, I picked one.

Later, A found out that I owned a car and tried to be friends with me (she gave me a call everyday). She also invited me to some events.

At one of the events with A, a guy approached me and we started talking. A joined the conversation and suddenly started talking bad about me saying that I might know the night life far better than her because I was always going out with different guys. In fact, it was the opposite. I was pissed and left the event.

Later, A called me multiple times. The first message was accusing me for leaving her alone at the event. The second message was an apology saying that she had asked B about this incident and B had said that she was bad to me. I wasn't bothered to answer either of these calls. I just cut her out.

A couple of weeks later, I've gotten a request from B that A wanted to get her earring back from me. The earring thing was months ago. It was a petty request but I just gave it B.

Should I just throw it away and not give it to her? Why did I bother to give it back to her? Any thoughts?

I wanted to hear others' thoughts just in case similar things happen in the future (hope not but it seems the world is full of this kind of things).