Most Helpful Girl
This is just a thought, I wonder if she is also upset over the break up and going back on line is her way of coping with it by chatting to other people or men so it takes her mind off it. If she does end up finding someone new on there it may just be a rebound relationship and they very rarely work out.
If you thinking of maybe getting back with her one day, then disappear from her radar for a week or two and don't answer her text or calls, she will wonder about you when she had some alone time and when she does that's when she will contact you, this is when you need to be strong and not reply for a while. What you need to do is keep busy, be with friends and when your ready address what went wrong with the two of you and be clear in your head of your answer because if/when she does contact you, you will be in a better place to answer and make things clear as to what you want.
Ask yourself this...at the end of the relationship was she still the same girl you fell for or had she changed.
I hope this helps a little for you, All the best and keep smiling.