Is it right that I do not get closer to this woman?

Ok she is my sister in law and actually she is really friendly and nice ot my family but there have been a couple of occasions where I thought she was sort of 'mean' or setting the terms of the relationship and I didn't want a part of that so now I keep my distance and keep her at arms length. So I am a shy person but if I offer to help or do something nice she would say 'you just stay quiet' and she is sort of 'fake laughing' and she catches my hands and sort of throws them at me which I felt was sort of a feeling of rejection and 'you're worthless' kind of gesture (nobody listens to me when I speak in the family as i am the youngest so I am sort of powerless in that regard and I felt she saw that dynamic and took advantage of it). And, sometimes if she is talking to my mom in the kitchen about groceries or something and I interject to speak (not rudely but when there is a lull in the conversation) to say something as I worked in a supermarket for a few months so I have an idea even if I am still living at home at the minute while getting my grad degree and she would halt me with her hand, ignore me and start yapping away to my mother because she has the power to do that in the family dynamic. I thought it was really rude and she was kind of being an . From these two incidents I just decided that I did not want to be her 'friend' because it inevitably means for me to be this person that she disrespects with impunity because my family could not care less (they would do it too)..My mother gives me grief now when she calls over because I hardly give her the time of day. I am civil and nice and polite when I see her. I may even chat or listen to her chat as she is very talkative but generally I keep my distance because I think she will disrespect me in the future.