She could get a power shower, although I suspect Owain is right, I have a
direct water heater and find I have to turn up the heat in winter to
compensate for colder water being fed to the house, which causes a drop in
pressure. I don't recommend connecting to the hot water supply as if you are
fed by a hot water tank, you rely on gravity feed which gives very little
pressure. If you have a diirect water heater or combi boiler you will have
the same problem in winter as you have with the electric shower.