Hiding Anxiety Issues

My best friend (since the 4th grade, over 9 years) has always been the more closed off type. She always talks to me once I question her a bit which usually turns out well bc I give advice that usually helps.

I asked her what she was doing the next day and she said she had a doctors appointment. Then she refused to tell me why. I found out she wanted to go in for anxiety and maybe depression. I felt really offended at first and then found out she told a guy she has been hanging out with for a few weeks with who is 10 years older than her. Even my boyfriend had a clue about what was going on. Like what!?!? I mean really!? I get that she probably had a lot of emotions about telling me but two guys over telling me!?! I just feel really hurt. I don't understand it. One of her excuses was that I have never come to her with a dr appointments BUT I HAVE NEVER HAD ONE. And for sure my boyfriend hasn't, yet he knew. Idk, I know she deserves privacy and being able to talk to who ever she feels confortable with. But that doesn't make it sting any less....