This is a really tricky one. The fact she went to a councelor and not turn to you suggest that she wanted this matter to stay confidential. We don't know what really went on, so it's easy to assume the worst. It could just simply be that she needed to vent, to tell someone. She's 15 now and becoming older, and thus wants more privacy. To be honest there's things in my childhood that I would have been mortified if my parents found out about. There's so much percieved guilt involved.
What happened in the past happened when they were children. What concerns me is the recent texting because she's a teenager now, while he's an adult. I've been in a similar position myself. The texts may have been innocent and well meaning, but if they were not wanted it would have felt very invasive (speaking from my own experience).
Just comfort her and tell her that she can tell you anything. But be patient and expect to wait. She'll tell her you in her own time.
BT: You've given so much great advice, it's a shame you can't take it yourself. I hope you can reach a point in your life when you feel better.
She needs to confide in you. And there is always the option of questioning the cousin himself. I am afraid that she might feel that she was molested, or that she in fact was, and that's why she talked to a counselor in the first place. So, don't let that option down, that she actually had been. I would talk to her a.s.a.p and tell her that i love her dearly and that there is nothing that she can say that i shall not understand and that if anything happened it is not her fault. It would be a good thing if you had an example of something your own, that she doesn't know, so she get's more relaxed talking to you. You need to get to the bottom of this, find out the complete truth and then analyze what exactly happened and what needs to be done, primarily to help your daughter.
..just to add that I probably will not come to this forum anymore. And want to say goodbye to everybody. The thing is that each time I read a story like this I completely destroy myself inside. Because of what happened to me with my brother, it's like I feel responsible for every person that was ever "molested" and try to compare myself to the case, obsessing about it. And each time I get a progress of leaving the guilty emotions in my life, a new story that I read shatters my peace and I start thinking depression or even suicide again. This is not normal and it will destroy me. But I hope that those that remain will continue to help and write to all of the new ones that arrive. Cause I will never forget how much you helped (or at least tried) to help me.