My best friend and the guy I'm seeing have a thing going on

Hi guys,
So I guess this will be a venting session but my best friend and I recently got into a dispute? Honestly she has a branch shoved up her ass so she has a problem with me. She's been hooked on the same guy since high school. Her "best friend" fucked him knowing she liked him and she's still friends with the girl. Unfortunately, I have tried multiple times to talk to her about it and I've told her she's better than this guy and can do so much better and is worth more I've done it for so long and she has started to string along boys and deliberately states she is putting her life on hold for this guy from high school. So this weekend I told her yet again she is better than that guy etc. how she will listen to her other friends that say the same thing I do and not me. But this weekend she threw out that "you don't need to lecture me about my person. I could lecture you about _____ but I don't."
So now my guy went on vacation and we aren't officially dating but it's been two years it's not like we don't have feelings for each other but we are both at a point in our lives where we don't want the title of a relationship. 
But, she's been on my guys case. Wanting to invite him every opportunity her and I are supposed to do something and even small get always she tells me to ask him. I don't think he has any intentions towards her, he is very nice to her but when it comes down to answering me he doesn't do it very often but will answer her if she texts him. It makes me nervous because I've been in a situation before where my "best friend" sabotaged my relationship and I ended it. 
However, she's going to the point where now she in a group chat with me and him and flirts with him openly and it is bothering me that he hasn't reached out to me being concerned as to why I am not answering or if I'm alright and she now has complete power with sabotaging something that's been pretty good for me. 
I can't text him because like I said he is on vacation for the next two weeks and I don't want to do it over text in case it doesn't translate well. And I can't necessarily confront her about it because well, she will sabotage my relationship with the guy. I know the way she is and I've lived with her and seen what she's capable of towards other friends and how vindictive she can be. And it's actually not like my guy is without blame either, I was very upset when I saw their text messages between each other. I did not appreciate it and my gut feeling is telling me something is going on between them. 
I just need advice on what step to take next. I want to wait and talk to him when I see him but I'm scared and nervous tat the longer I wait to confront him the worse it's going to be on me. So I'm doomed if I do I'm doomed if I don't.
Please no negative comments about myself, I had a situation like this once before and I just need some thoughts on this maybe someone has better ideas than I do and I'd appreciate them. 
Thanks!