PatriotsRule,
The more you care about it, the more you push her towards it.
The best way to address things like this is to not address them at all. The only time something should ever be addressed by you is if you actually catch her in the act of "cheating" on you (i.e. sexual contact, kissing, sexting, etc).
If your girl is crazy about you, then some dude texting her non-stop isn't going to change that. If that guy is able to convince her over text messages that she should dump you and be with him, then it means there were a host of other problems going on in your relationship that needed to be resolved by you, but they were not resolved. For example, maybe there has been a lack of sex, or the sex you've been giving her hasn't recently resulted in orgasms. Or maybe she's noticed that you're becoming needy (by getting upset or jealous every time she talks to a guy that isn't you).
For most guys, they don't even realize why a girl would do this. Maybe you've stopped going to the gym since she became your girlfriend and she has not, so suddenly you're not the same guy she started dating at the beginning. Maybe you've been letting her win arguments because you're afraid of what would happen if you put your foot down. There are a lot of reasons things can start to go sour. But having a guy talking to your girl should never be an issue if she's fully in love with you. But maintaining her attraction, and love, in a relationship still requires you to put in effort.
If you feel like you're putting in the effort necessary to maintain her attraction, then that guy who is texting her will forever be the "dude who texts my girlfriend hoping something will happen." If you don't put in the effort to maintain her attraction, then that's the only time it could ever become something more... and in that scenario, the only person you could blame for that would be yourself.
- Franco
