Hi there.
First of all I think it speaks well of you that her pleasure is important. Sometimes for a woman to have satisfying intimacy the issue has to do with trust and a feeling of emotional safety. This does not mean the issue is about you. It could be something within herself that needs support. Unless there is medical reason then you probably want to consider her emotional pleasure zone.
I am not a medical person nor am I qualified to give advice. This is just a suggestion.