Insecurities

My partner and I have been together for 13 years now. Its great now, however in 2015 we had a huge fall out that involved another person that he got close to and it started out with them being friends. I was going through a hard time and seemed to have pushed him away. We have gotten over that and things got better. The problem now is that he does have new friends, particularly one that's very close. I've met her, we've spoken, she buys our kid gifts and she is a really nice person. I don't feel that she has another motive or anything and my partner has reassured me about this many times. I trust it. The issue is that it has started to bother me that they chat, every day. About whatevers going on in the day and I'm sure it's totally innocent. But she sends him photos of herself, nothing bad, but of the clothes she's wearing that day or something like that. I'm uncomfortable with that but I keep telling myself that it's because of the past experience of getting close to a friend. I am not sure if they are too close by sending pictures of herself or am I just overreacting?