Go ahead and tell her to take the filter out....a filter is only beneficial for cycling, and you can't cycle a 1.5 gallon. She should do a full water change three times a week in a tank that small, and remind to her not forget the water conditioner! That stuff is really important.
If theres any way to get a pic of him, that would be very helpful...
But for now, she should probably do a full water change, rinse everything thoroughly in hot water, refill the tank with water the same temp as the water she took out, add water conditioner, and slowly accumulate the little guy back in. She can also go pick up some aquarium salt, completely dissolve about a teaspoon in some hot water, and add that too the tank and that will help.
Also-Is there a thermometer in the tank? If not, definitely go get one so you can monitor the water temperature and make sure the heater is working properly.