Not a revolting Q! Just start playing a little bit then ask her why? How strong is your relationship? Will she listen to you? Get her to talking. Be prepared for whatever she might say. Listen with interest. You might both learn something from this...
When "No" doesn't mean NO then you have to have a safe word she can use to mean "I really want you to stop now". And when she really wants you to stop then STOP.
All I Have to say is make sure your very clear about what you want as a couple. It can get out of hand if you don't have certain rules in place.
Read my story black and blue pts1 and 2 - use what u need