Marriage, Massage & Opposite Gender Friend

My wife and I have been married for around 5 years, together for close to 10 years. When we met, she was a fitness instructor and recently decided to get her massage therapy license to add to her skillset. While in school she met someone she clicked with, a guy we'll call Dan. She has described Dan as a younger looking version of me, nice and someone she wants to be friends with. My wife and I have been going through a bit of a rough patch lately but actively working on it. However, I told her that this friendship with dan made me uncomfortable. I might be a bit old fashioned when it comes to opposite gender friends in a marriage but when you add massage to the mix it gets harder for me to not be upset. When I told her pursuing this friendship made me uncomfortable she pushed back a bit but otherwise dropped it. I made the mistake of looking through her phone and found out she has invited him out to her work for a massage on multiple occasions, without telling me, and he agreed to come to her work today for a massage. She made no mention of it to me. Do i have a right to be mad? If she weren't a massage therapist, a massage from another man or for another man would be a hard no boundary for me but not that she's a therapist, the line seems fuzzier. I realize men and women can be friends platonically but this just feels like a breach of trust by not keeping me in the loop about her invitation. Thoughts?