With regard to punctuation and grammar please read some Cormack McCarthy. Not to start a fight but we have a bald brother in pain and sometimes when people are in pain their absolute last concern is spelling and punctuation. So the poor guy comes here to get a few words of advice and gets some shame instead. Let's reign in our high horses, gents.
Rocko, I hope that you can understand that this whole thing is not totally about your fiance. Part of the problem here is about you, too. Not that you are the problem, don't get me wrong. What I'm saying here is that if something like this is bothering you this much then it is not totally about your fiance flirting on the internet. It is as much about something that happened in your life at some time that causes you to have trust issues with this person that you want to have a relationship with, or creates a disbelief on your part that you are sufficient to maintain the relationship.
Check out some counselling before the wedding, seriously, to make sure that you have all of your ducks in a row. Maybe you will find out that this girl is not the right one for you or maybe you will find out that you, yourself, are not ready to get married to her or anybody else at this point in time. But the important thing is to check it out.