My mom makes me feel bad bout my legs?

I'm not fat, but I'm really muscular, especially my legs. I do probly have some fat there, but I actually have a small butt, just thick legs. So I went to get short with my mom and I put on a pair that were kind of stretchy denim. She said they were too small even though they were comfortable and were honestly not sqeezing anything. She brought back a pair for me to try that was 3 sizes bigger, gapping in the back and said they fit perfectly. I showed her the back and she said wear a belt. :p I didn't get them. She makes me feel so much bigger than I am. Normally I'm a 3 in pants and XS shirts, but compared to my 00 sister, I am. Sorry for the venting, advice? Thanks