What a kind thing for your sister to do. Even though the jelly roll has fabric in colors you don't like, challenge yourself to make a quilt for her with that jelly roll. When I've made reunion quilts, some of my relatives have sent me some bizzarre fabric when I haven't specified a color scheme, but they actually came out quite nice. Two quilts were made with the following fabric colors: red, navy, teal, purple, red, orange, green, and black. The first one I used the album block and the next a basket block, and they really turned out quite nice. On the second quilt I used a black fabric for the border, but used the wrong side which was a nice soft grey - it was beautiful. Sometimes you never know.