She has been talking to him for the entire time we have been together. The messages I saw were not pretty. They still say they love each other and miss each other. We have been together for a year.

How old are you both? Why have you not asked her directly what's up with those text messages? I would.

Well she is obviously not over her ex there's one thing being good friends with an ex and still being into your ex.You should sit her down and talk communication is key especially if your having trust issues