I caught my girlfriend stalking someone else this morning

This morning I woke up, and while preparing breakfast, I glanced over and saw she was looking at a woman's profile on her phone. Clearly, it was someone she knew, but I didn't say anything; I just kept it to myself. Now I’m thinking, should I ask about it, or am I just overanalyzing? Am I making something out of nothing, or is there something going on?