Sharing Our Innermost Thoughts

I just want to get this off my chest. Hopefully it will help.
I am 26 and I would honestly classify myself as a logical person.
I started my first job a year ago after finishing my masters and I work for a company which has business in multiple countries. Not wanting to discuss the exact places they are both in Europe within 2 hours flight time. During my work I met a woman, 28, who I immediately fell for just from conversation via Skype, we talked much during the summer time as there was a low in work quantity and I really developed feelings for her during this time, from our conversations she seemed to share them.
During early September I was on vacation and decided to use the “Oh I am worried about things at work excuse” and added her on Facebook. We talked a bit the first few days, quick responses, long talks, both in an out of work and I really thought this may lead somewhere. But she started taking a larger and larger amount of time to answer me outside of work hours, she told me she didn’t really use her phone much outside work so I, reluctantly, accepted this excuse, during one of the conversation we had at work she ended up just giving me her number and telling me to just put her in WhatsApp so she could answer more quickly, I found this odd but whatever, sure and added her, the behavior didn’t stop, 1, 2, 3 hours between messages, not even long ones either.
She tends to travel allot, I don’t as I never had much money and was only able to go to university due to a scholarship, and she told me she wanted to go to Cambodia some day to visit her father’s home country this in casual conversation. At the start of the month she told me she was going to Cambodia and Vietnam with some work colleagues, for a month. I though “hey thats fine”, a group of people going on vacation sure. Then this week she hit me with the travel plan, Thailand to Vietnam to Cambodia, ok go all this time see the area a bit. Then she tells me “O Ill be going with one guy for the first 2 weeks and then the others will join us.” this fucking broke me.
She knows this guy for 1 month, about the same time her cadence of responses began to fall down. This really brought me down today and I am just thinking if she just found another person and just didn’t tell me or she just didn’t like me from the start or if our relationship, if you can even call it that broke down at some point.
She is leaving my team at the beginning of next year to work with this guy’s team.
A little backstory why this trip really flips me:
The fact I am taking this this hard is, the city I live and work in is a popular tourist spot, so is hers but its massively more expensive, in August she was supposed to come with our team leader to work with us for a week, but since she decided to change team the team leader cut her of the trip as he couldn’t claim this was for team building purposes as she was going to leave. She didn’t tell me the reason she just told me she wasn’t coming so I asked the team leader why she couldn’t come and actively tried to get her to come. She ended up not comping and the team leader told me the reason why.
She then suggested “how about I go 1 week to your town and you take a week off and show me around”. I was obviously happy about this and agreed, she was supposed to tell me something and come Early October as the weather was still very much good this was still mid august. Now the month starts, messages die out, she cancels on me tells me she is going to Cambodia and now says she will go alone to Tailand and Vietnam with this guy for 2 weeks but she couldn’t come for a week…
I am going to meet her in the second week of December as I am going to her city for work. I don’t know what to do when I do see her,  wish her happiness because I really do? I just wish she was happy with me and not someone else.