Yes, I understand that cement-based grout can sometimes harbor mildew and mold in wet areas. Grout sealants may help somewhat. If she uses white grout, than it would be okay to use a mild bleach solution to combat the problem. If she uses a colored grout then bleach would be out of the question.

There is one grout, however, that claims to inhibit the growth of mold and mildew spores not only on the surface but throughout the depth of the grout. It is called TexRite grouts. I have not personally used it but it sounds like it might be a good solution to her problem.

www.texrite.com