I know it's a long post, but please read, I really need advice
About a month and a half ago, some girl I kinda knew from some forum added me on facebook. We started chatting and things were going really well, extremely well. She was really into me and it was really obvious. We were chatting for a few hours each day, and whenever we stopped and I logged back in after a few hours, a new message was waiting for me. She was really interested about me. I was not so enthusiastic, but I let her know that i liked her. I actually was enthusiastic, but I just didn't wanna seem to eager, so I played it cool. Since she lives not so near me, we arranged a meeting at the beginning of August, when she goes on vacation.
Anyway, things were going great for about 4 weeks. Then I noticed she slowed down, rarely messaged me, but still, if I messaged her, she would reply and we would chat normally, she didn't cut me of or anything. But she still gave me signs she liked me, told me she was excited about meeting me and can't wait, I asked if she was certainly coming so I can plan and reserve some things for our date and she said yes. She even gave me her phone number, out of the blue. So the lack of her messaging me I just interpreted as her wanting to spend some more time with her friends, before she leaves.
And then yesterday, she messaged me "sorry, I can't come". When I asked why, she said she thinks she's in love with somebody else. I asked her how long was it going on and some more stuff, but she didn't really wanna say anything, just that she knows him in person and that it wasn't anything I did, it just happened unexpectedly.
So basically my whole world collapsed. I was really looking forward to meet her. I really liked her, and she seemed really nice, I would never have expected her to do something like this. What hurts me even more, she literally cut me of. I asked her some more things, said it wasn't fair and that she should at least give me a chance and meet me in person but she doesn't wanna talk anymore. She sent me a few short messages, but basically for her it's over and she doesn't wanna talk ever again. She didn't remove me from friends, but made her profile hidden to me, so when I look at her profile, it's like we're not friends.
What is strange to me is that before she mentioned she doesn't want a boyfriend or anything serious, and when I asked what about us, she was like, we'll take it slow and see what happens. So it is a little weird that she is suddenly in love. I suspected that maybe things got to serious (date should have been in one week) and she got scared, I asked if that was it, but she sticks to the other guy story.
And for me it is really hard to except, because I really liked her and even more, she was like my best friend for the last month or so. We talked A LOT. She gave me since the very beginning a lot of signs she liked me, even a lot more that I would have expected and a lot more that I would think somebody I just met should give me. But I didn't mind, I enjoyed it. Now at the end I asked her if she really liked me and she said she did, before.
So even if she blew me off romantically, I am sad because she doesn't even wanna talk. We made a really good pair, had lots of fun, and now it's like nothing ever happened, like she never existed and we never talked.
So what do you think? Is the other guy story true? Or is she just scared? Should I message her again, try to get her back? What should I say? If she really had this guy for some time, why did she still give me signs she likes me? Why did she give me her phone number? Should I call (though she probably wouldn't reply)? Most importantly, what happened, why is she acting like this?
Sorry for the long post, but I really don't know what to do, I don't wanna lose her, but I am not sure if there is anything I can do