I think the key to avoid getting water into the workings of the crock pot is to minimize the amount of exposure to water.
The best way to do that is to make sure the liner is easily cleaned. I would suggest she fill the pot with hot soapy water and let it sit overnight. This will loosen any baked on food.
Dump this water out, propping the pot on the counter over the sink and using a scrubbie or dishrag, wipe out the liner until all the food is rinsed out.
Dip a dishrag or scrubbie in soapy water and scrub the liner, allowing the soapy suds to drip out of the pot into the sink.
Once clean, rinse and drain.
A little water dripped on the outside or even into the electrical parts will not cause any harm so long as the pot isn't plugged in until all the water has evaporated. Obviously, the less water that's accidentaly dripped the better.
When she's washing the crock pot, tell her to make sure the control knob and the place where the wire goes in is NOT at the bottom when she has the crockpot on it's side while washing or draining.