I'm going to turn off my roommate's space heater while she's gone
What makes you want to turn off her space heater?
I can see no reason in leaving it on.
The high power demand of the space heater can cause it overheat, potentially causing a fire. Turning off power will save the energy needed for other parts of the city.
Exactly my point.
That's really good you want to save power. Maybe you can set it up with a smart plug or a timer. That way it turns off right when she leave and can program to start it again before she arrives at home.