How to start rebuilding? - 2

[Hoju]

Why can't I just move on? There is a very attractive girl at work who keeps throwing herself at me. We've been friends for years and laugh all the time as well as share many of the same interests. Why am I not excited to get to know her better? Get to know her family and friends? Or even simply just sleep with her? I feel nothing for her, I enjoy our time together but if she quit tomorrow and I never saw her again I wouldn't care.

My W cheated on me, she is happily with someone else, what's wrong with me? why can't I just let it go and move on?