You are clearly obsessing about her. Did you get any sleep last night? Or were your thoughts going around and around in your head, making you feel more and more helpless and out of control, and thinking that the only thing you can do is to cut her off?
She is probably feeling smothered. She’s scared because it’s too intense. She wants to run away, and people usually use an addiction of one kind or another to run away. Addictions could be to drink or drugs or work or RPGs or sex or love. So she could be turning to others as a way to distance herself from her fears of being smothered.
At the same time as she is afraid of being smothered, she is probably also afraid of being abandoned. This is an unconscious fear, but it also can lead her back to you—but only after you actually have cut her off.
It’s an unhealthy, but typical pattern. It arises out of abandonment as children—for both parties. Childhood abandonment can be literal (a parent disappears), or more subtle—the parent is not available due to an addiction or workaholism or something else.
Reactions to this abandonment can go a couple of ways. One way is to desperately seek love, and particularly the high of falling in love. But then it falls apart because one believes one is essentially worthless, so who, in their right mind, would love me?
The other way is to seek out a very enmeshed love relationship, and then push it away because it is too dangerous. The love may abandon you yet again.
There are many variations on this pattern, but that’s kind of it in a nutshell—as far as I understand it.
What can you do about it? Therapy for one thing. Understanding the pattern and looking for opportunities to break it. On your side, learning how to not be so obsessed and on her side learning to trust more, and not run. You must try not to reach out ever more strongly the more she disappears.
These are long term things. At this moment, you are probably so anxious you can’t imagine pulling back. You absolutely need to know what is going on with her. You think you will die if she will never be in your arms any more. You want that high back—being totally in love with each other and unable to separate. Loving forever.
In the short run, focusing on cybersex will almost certainly guarantee an end to the relationship. If you understand that it is merely a symptom of something much deeper, perhaps you can get beyond that. But focusing on the transgressions just fuels the flames of passion. You need to douse that fire if you are to save the relationship. You can’t afford, I think, to spend any energy worrying about cybersex. It’s just a symbol of her pulling back.
To work on your relationship, contrary to the myth of love, you have to reduce the passion. This will allow you both to think straighter and to communicate more effectively. In the long run, that’s what will save the relationship. I wish you luck. I’m like you. I am addicted to love and passion. I need to pull back, too, or I’ll destroy everything I value in life.