Is it a temporary split; ie due to injury or is it a permanent one; continually splits no matter what she does?
If its the first then I would either do a silk or fiberglass repair together with shellac until the split has grown out. She could then continue her normal nail routine after that.
If its the second then I would do something similar to the first option but you'd have to tell her that it will never "be fixed" and as long as she carried on with the protection then the nail should be fairly trouble free. I've also had very good results with permanent splits using Brisa Lite under Shellac and have, in some cases, had better results.
HTH
Karaxxx