Tawi is correct my friend. She could have a number of reasons for this. One is that these men each sent her an invite to facebook. So when she does actually join, with the same email address - they are automatically her friends!
And if she is still talking to them, what does it mean? Are you engaged? You say you have been talking for 4 months and you plan to go over in October! Does she take you seriously?
Remember, she has more to lose than you do at this stage in the relationship. Speak to her but try not to get angry with her. Just ask and she will explain.
I know the girl I am seeing now had at least 2 other guy's interested in her. So what! Take a look below at her picture, a lot of guy's should be interested in her She also had a myspace page she never told me about.. Again, so what. It is old and only 1 friend on it with littl else. Probably forgotten about in the last so many months.. In all seriousness, Go to see her in October! Spend time with her and see how things pan out, if it is not meant to be, you had a nice holiday with a pretty lady. It's all good!