Opinions???

So about 2 years ago I went through my boyfriends phone and he was planning to cheat on me with this girl and hung out with her for a whole month while I was away with my family. He said he never cheated and I don't know if he did or not but it did hurt knowing he was planning it. Him and the girl are still friends and she is actually my friend from

High school and he sees nothing wrong with being her friend. Recently he got her a job at his work and has been texting her a bit. I don't know if I'm being crazy or not but am I the only one that thinks that's wrong or????