What she needs is a 'system' rather than just a pump. Yes they are safe. They are called hot water recirculation systems. Many companies make them They consist of at least three parts: a pump, a checkvalve, and a cross-over. At least one company makes one that has all three parts in one box. If you search here, you'll find various discussions on these. Yes, they do work, and I have one in my home. There are retrofit systems that don't need a lot of installation, and there are similar (sometimes the same) system that can be installed when the house is built. It works best with a dedicated return line to the WH, but most retrofit systems use the cold line. Lang, Watts, Grundfos, RedyTemp, and others make systems that have (essentially) all the stuff you need to install other than maybe some plumbing fittings. They all need to be plugged in, so the pump needs to go somewhere near where there's power, or run it to the area.