Elastic waist pants are one of the easiest things to sew, and as you get better you can add a lot of details like pockets, topstitching, etc.
You could probably find some lightweight denim and make her some that look more like actual jeans, topstitched with that yellow/gold jeans thread, if she misses jeans.
I can see a lot of fun variations, really. Cuffs of contrasting fabric, patch pockets with cool buttons, iron-on patches, etc.
ETA : I had a skirt made out of tencel denim that was very soft, so that might be a good option (if you can find it on the bolt) if you wanted to try denim.