Hi Shedd
It makes sense to feel hurt when people talk about an ex partner dating someone in a conversation, especially after a breakup. It didn't work between two people, and it makes sense to feel some sense loss. When one person is thought of to be dating a later, and different person, that sense of loss can feel more real.
If you're not getting too upset over it--yes I do think that can be seen as a indication of detachment. Or being "over her". When we have successfully detached from a relationship, it may feel better because we can experience that life is okay or better in this state. It does seem to have a comforting effect.
I hope things go well for your interview.