i have a issue

Me and my girlfriend have recently got back together after a break up that lasted the whole summer. I was the one who broke up with her, thinking that my love for her was not reciprocated. During the breakup we exchanged letters and, even though I tried to get over her, I couldn't. I think she is the love of my life. We have both been so happy since we got back together. We talked a lot about issues we had in the past and improved our communication so much and I thought this could really work.

Well, until she went on vacation on the other side of the world a few days ago.

I was happy she was going on holiday because she has been very stressed with work and I thought she deserved a break, and I thought she booked it while we weren't together. But she was weirdly vague about the people she would go with, almost defensive. She just said "some friends." I didn't think much of it, I just thought it would be friends from her old job that I hadn't met yet.

We'd been messaging since the beginning of the holiday, telling each other that we miss each other and being cheesy. She would tell me about her day and I would tell her about mine, as we always did.

Until I looked at her "tagged" pictures on instagram.

She went on holiday on the other side of the world... with her ex?

Now, we did talk about her ex when we got back together. They are friends. I am very open-minded, I'm not the kind of girl who would tell her to cut contacts with her or stuff like that. But she is so weirdly secretive about her. I literally found out they were still friends by looking through her social media, and she never tells me when she goes out with her. I told her I would prefer her to be honest about this, but she kind of made me understand she didn't want to make me feel uncomfortable and she would rather avoid this kind of conversation.

Well, fair enough. But I don't think this is the kind of conversation that should be avoided in a healthy relationship.

You don't have to tell me you're going for lunch with your friend who also happens to be your ex, I guess, but - tell me if I'm being overdramatic here - I think I should know if you're going on a holiday with her!

The thing that really, really, really hurts is the lie.

"Some friends?"

First of all, how oblivious does she think I am?

And second, what the actual f*ck?

I have been crying for the past three days and I also have anxiety so this isn't really helping. I don't want to talk to her until she's back and I've been very cold in my replies to her messages. She has been very sweet, sending me emails and commenting on all of my pictures and telling me she misses me, but I just can't do the same right now. She got annoyed because of my short replies and because I wouldn't tell her what's wrong, so she is now giving me the silent treatment.

She genuinely has no clue why I am acting like this.

I am so hurt but I still don't want to ruin her holiday.

I don't know what to do, to be honest. This is just too painful, but I still want to make our relationship work, more than anything. I still love her, but I gave her my whole trust and she just lied.

What should I do?