If we have been chatting friendly for a while already, then flattered. It's clearly implying that from their perspective I appear to be very desirable. And if

If we have been chatting friendly for a while already, then flattered. It's clearly implying that from their perspective I appear to be very desirable. And if it was a serious question asked early on, I would probably reply with something I don't like about myself, a weakness, if you will. It's not an entirely unreasonable question.