This is definitely not a pleasant situation to be in.
“Countries known for their sexually aggressive men”. ~ Jerry Smith 
Whats your take on her friends? Friends tend to drag you down into their vices and virtues.
I highly doubt that this trend of going to these countries is for the pure pleasure of cultural appreciation, as they are historically rich civilizations after all. Considering that this trend is popular after military service, you know, when you’ve been dry for a while and need to blow steam.
She does drink, doesn’t she? Or her friends? Then go to a bar and a club? “I was drunk, he was hot and cute, we had a fight that day, one thing led to another, and I slipped on the peel. etc…”
What does that mean, by the way, to you? Committed and married in the future, what’s been stopping y’all? How old are both of you, anyway? All these commitments, marriages, children, assets and life built together does not guarantee a squat; many a men have ended up in a living hell because of these kinds of beliefs, bankruptcy, homelessness, suicide, depression and mental illnesses, and even jail.
I’m not putting ideas into your head, as your gut already seems to be telling you something, else you wouldn’t be posting this in this forum. However, reality of the matter, this is not a unique situation and it happened, has happened and will continue to happen, often times the outcome is the same; I’d say worse since its a 2-3 months. What is she a nun?
One approach is a sort of an ultimatum, and depending on her maturity and how much she does actually love you, in other words, how valuable you are, it will backfire in your face, so I’d suggest not going for it, but just in case it did:
You could always put your foot down and tell her what you think about the situation and this will tell you right away if she’s gonna be sticking around for the long term, do it in a mature manner, think how one would tackle this situation if they were on a status/romance title (indifferent). Afterwards, you suggest going on a trip together and have fun together, you do seem like you want her to have a great time and enjoy life, after all
? This is a sort of skip through the BS, no time wasting approach.
You could also be cool with it her going on her 3 months girl trip, I’m shaking my head and sighing as I write this, because I’ve heard of Vegas weekends or girl weekend, but not almost a whole season. Sweet Jesus, man, that’s like one of the worst long distance relationship ever. Back to my point, if you are going to be cool with her going, and that’s the outcome that I’m predicting; then, remain INDIFFERENT. Do NOT ever, show your insecurity, and if you do show it, or have, then learn that that’s there within you and needs to be eliminated, because all of this is about your growth.
Knowing that if woman wanted to cheat, She. Will. Cheat. Where there is a will, there is a way. Even if you locked her in a closet. So don’t be possessive as if she is the last piece in the store, or fish in the pond, or whatever metaphor you fancy.
How’s your sex life, btw? Her eyes are still en-flamed by passion and her womb longs for ya? The fires wane in time, but you two seem young for that.
One last advice, do yourself a great favor, and let go of that nonsense of equating time and commitment with faithfulness and fidelity. Never been thing. Humans are humans. Keep working towards your goals and do not prance around the house wondering about her, get busy.