Weird manager...

So, my other half started a new job a few months ago and he forever talks about his manager who is female. She compliments him a lot and he won’t stop talking about it, he’s told me how nice and how funny she is. She emails him and calls him a lot throughout the day and before anyone comes at me I know that she is his manager but there seems to be flirting going on within the emails and he talks about her how he use to talk about me😞 I may just be overreacting but when I spoke to him about this he got on his back foot and started acting weird, I love that he likes his job and that he is happy but he seems to like his job more than he likes being at home, we have a really good relationship and I have no other issues but this. As I said I may genuinely be over reacting but it’s just the way he talks about her and the way she talks to him, it kinda makes me a bit worried. Please tell me if I’m wrong. Also if he tells me he is having a bad day at work he is so quick to tell me that it isn’t the people who he works for it’s the job, when I never insisted it was in the first place, he just told me she is helping him cheat on a test that he needs to do, it just all seems a little too friendly....