Had one girlfriend that had an orgasm every few minutes by fucking, fingering, getting eaten out, masturbation... Basically every kind of sex made her come immediately. She really was a miracle. One day she came 40 times in a row. I counted intentionally that day because I was wondering how often she could come. We only stopped that day because I was completely done and exhausted and drained.
Yeah, it's tough when no matter how much you try it just won't happen. Had a girlfriend once that seemed to actively avoid getting there, she would clench her highs around my hand so I couldn't move anymore and stuff like that every time she got close