The question is, why did she even bring the subject up in the first place. It is kind of a weird thing to talk to a any co-worker about but especially a male co-worker. Here is my take, some times even happily married people can have a bit of a crush on someone else; this, I suspect, is the answer.
That said, I will give the same advice as everyone else. Drop it. It's not really worth taking it any further.