Sounds like she said Kenny.
She was probably thinking about him, imagining it was him or maybe just focusing on a memory of him.
It doesn't necessarily mean she is still in love with him.
It doesn't necessarily mean she wants to drop you and get back with him.
It doesn't even necessarily mean she often thinks about him when she is with you.
All it means is that she was thinking of him at that time.
If you want to be a man for her and not come off like an insecure baby then you won't make a big deal about it. Cripes he was her boyfriend for 4 years. If she does it again then you can make a big deal.