I don’t know the personality of your partner but it might help to explain why you need her to communicate with you about this. Usually it’s because you want to understand what her feelings are etc but I suggest you instead give the reason why you personally want to communicate about this. It makes it more relevant if it comes from you.
Another thing to do is when she says “Whatever you want” tell her directly that what you want is to communicate about this. I consider that to be a fun way of saying you want to talk about it while still in the D/s “character” so to speak and still being serious about it.
I would personally try the second first than if she still resists go with the more direct method.