I do not waste money on anything that unnecessarily adds to land fill.
Has your girl tried slowly removing the sensor in the shower.
Get it very very wet, start to peel off the backing a little bit, let the water permeate the glue where it has started to peel and then slowly remove it.
I may get a small black ring which comes off with shower gel and a gentle pumice (some people use baby oil) but no other problem removing it and no reaction to my skin. And saves money. And reduces rubbish.