Welcome to the forum, TimTim and IronFeather, it's invaluable to hear female perspectives.
I never knew there was a female analogue of premature ejaculation or that women also have NE's. Time to learn.
I have a self-conflicting view on overmasturbation and POIS. On the one hand, it is clear to me that overmasturbation does not on its own cause POIS, since if that were the case, POIS would be a widespread disease and not a rare one. Really a lot of men overmasturbate, I've never considered myself one of them. In fact, perhaps I have undermasturbated at times. On the other hand, the one time in my life when I overdid it, that's exactly when my POIS started. I remember that day: once a girl texted me with a clear signal we'll hook up in the evening, I masturbated at least once (maybe twice, this I don't recall) in the early afternoon in order not to do my usual terribly quick performance. Then with her in the evening, I did come quickly the first time, as usual. And I couldn't do it a second time at all, I didn't get aroused despite efforts. The next morning was the first time I felt POIS.