Probably, although it would probably have been a pretty small one if she was running it from an extension cord. Depends on the circuit and the cord, I suppose.
Being a commercial building like that it was probably connected to a 20-amp outlet. However, most people use extension cords that are not really adequate.
An electric blanket would use less energy and keep one warm.Several ordinaty blankets and good sleeping bag would allow comfortable sleep.Sanitary needs could be achieved with modest sized containers to be discreetly emptied elsewhere.Being aware of public restrooms and avoiding being noticed too often as well.Heat rises so heat from main building may have made space tolerable.
Reminds me of characters in fiction who lived in the hidden spaces as they feared the “authorities” AND the criminals.