Please give me some advice?

Ever since I've been married to my hubby,his sis doesn't seem to like me. It feels like she is always indirectly undermining my efforts by commenting how great others are, actually using qualities that I have, such as having soft silky hair, getting 1st cles in all my ignments etc. I am a psychology grad and she is an accounts student. At first I thought it was a bit of sis in law jealousy, but she seems so chummy with her other sis in laws, just not me! My husbands brothers wives are not educated nor are they the least bit attractive, so I thought maybe she feels threatened by me. But why me? I am not someone to compete with, I am her bro's wife! The other day I was putting on my eyeliner, she was with her cousin sis and she said how her cousin is lucky because she has beautiful eyes, so she doesn't need eyeliner, I felt so small by what she said, in a way I felt ugly. Please help me because I am at breaking point. Thankyou