I was actually always afraid to use retinol because I didn't understand it. I started using it when I was 34. For anyone one new to retinol or any actives in general, start off gentle. I started off using the CeraVe resurfacing retinol serum and still love immensely. I'm currently using the Naturium retinol complex serum which has bakuchiol in it as well which may make this one a bit more gentler. Regardless of what she uses, always start off slowly so that the skin can acclimate and the barrier isn't compromised. I would say once every 3 days and then go from there depending on tolerance. Hope this was helpful. Good luck!