She should read the newbie 101 thread at the top of the forums. It has some advice that can help beginners. The biggest thing is to avoid eating even tiny amounts of gluten. The celiac reaction is auto-immune and it only takes a very small amount of gluten to kick off the reaction. The gut can't heal while the immune reaction is ongoing. So she can't fully absorb nutrients until the reaction stops and she has some time to heal. The immune reaction may take months to stop completely.
A good diet to follow is whole foods cooked at home, and avoiding most processed foods. Some people can't eat dairy without issues for about 6 months or so.