Happens to me a lot too
I think it's because I'm female, and the gung-ho young bucks simply don't want to train with a girl
I remember training with a fairly senior lady who I initially found somewhat frustrating. She was very good and could do techniques with me quite easily, even though I was significantly larger and heavier and was applying my strength.
However, when I was nage, it initially felt that if I so much as twitched, then she threw herself - so I never got to actually feel any resistance at all to the technique. I realised that she had most likely developed this response in self preservation with lots of practice with gung ho guys. I started getting much more value when I approached techniques much more softly and in a spirit of research, to see if I could control things to the point that she didn't just roll away. Adjust your practice to your partner - look at what you can learn from everyone.
Mind you I have known some scary ladies too, who have challenged more than one keen young bloke and shown them the error of their ways!