She sounds like a sweet girl who couldn't hurt a fly, and it seems that she is willing to do more than the usual for you. Maybe she is too afraid to hurt you? Tell her that it is not that easy to hurt a man.
You can also intent to ease into the wrestling. First cuddeling in bed, then wrestling in bed - meanwhile you can calmly give her directions, just don't expect her to get it rightaway, it might take some time until she does it on her own. I mean, girls giving us directions isn't easy either
For quite a long time I had the same frustrating experience of not beeing able to finish with regular sex. Even when I did, it was like climbing a mountain without the joy when you reach the top. It always got easier the better I was in sync with her. (Also, there are some herbal remedies that enhance the experience...)
You already opened up to her, so she won't think your a jackass when you continue trying. Just don't get angry at her, after all, it is not her fault (nor yours).