Rhinestones are not going to fix the fact that the pattern doesn't even tell you how to make a proper crotch. The instructions tell you to cut out a piece of jersey fabric against the template, lay it on the underwear and stitch in place. The result is that all of the hems and the raw edges show.
One of my other issues with this pattern is that one of the knicker patterns is shown with scallops. You are supposed to buy fabric with scallops that perfectly matches the pattern. I used lacy scallop fabric, but had to improvise on the pattern because theirs just didn't work.
The knickers ended up turning out nice as I took extra care to match the lace stripes in the behind view and carefully cut out the lacy scallops, but especially with the advised crotch construction, I can't see how these will last more than a few washes.
Extremely Crafty suggestion - Don't buy this pattern.