Girlfriend sleeping w/male friend in same hote room

[Pertemba]

My g/f and I have been together for 4 months (I know is just little time), but since before we met she had
already planned to go to Europe with a male who used to be a neighbor, according to her,
just a friend, nothing ever happened between them. They met in Europe and shared
the same hotel room the first night, then they stayed in different hotels as they traveled along, then they met a female French friend who she stayed up with until now, but tomorrow
this female friend is going back home and my g/f will continue traveling for 4 more days
with this male friend (who lives in another state and I have never met) and continue sharing a hotel room before they come back, to save money according to her.
This is the situation, it bothers me big time, I feel I trust her, since she’s proven to me during these 3 months together, how close we have grown, but at the same time she’s gained my trust since she’s so old fashioned in many ways. What what’s bothers me
Is the fact that she never took the time to ask me if this felt alright w/me, for her it was
a matter of fact, She had mentioned this to me before but tried to show her how secure
and strong I was by not showing any disagreement or disapproval. I regret not making a stand on how unhappy this makes me. But now knowing she’s w/him in the same hotel room I’m running thru this gamut of emotions, anger among them. Three days after departure though, she called to say how much she’s thinking about me and that she wishes this male friend was me instead, that is not the same. I told her among other things casually on the phone when she called that I wasn’t happy at all she was doing that anyway, to what she reply, him? “You need no worry, me and him could never be together ever, there’s a better chance that me and my female friend do something if you’re gonna worry about something, but then again I’m not a lesbian.” And that she’d love to come with my in my vacation in two months.
What should I do? Should I confront her politely on this when she’s back or just let it be.? Right now I feel I want to turn the tables on her just to make her feel what I’m feeling now, this terrible pain.
I know in my heart that if I would’ve been her instead I would’ve changed plans
Or at least I would’ve asked her if she was ok with it.
Comments?