First did you or didn't you sign a lease?
When you sign a lease the landlord is allowed to raise the rent only once when you sign a lease. When the lease is up the landlord can raise the rent to any amount they want to. The heat lights do suck up some watts. Being she knows about what the average consumption of power is that's how she figured it out.
Heres what you could do when she wants to see if you have your heat lights on. You could tell her that they haven't been on for a while and just leave the heat pads on when she's around because she can't see if they're on. What I do sometimes is turn the lights off during the day because my home is very hot inside in the daytime it keeps the temperature pretty level. So when she's not around @ night just turn them back on....lol
My Snakes (1)Eunectes Notaeus, (1)Python Reticulatus, (1)Eunectes Murinus, (1)Acrantophis Dumerilli, (1)Boa Constrictor, (1)Python sebae, (1)Striped
Morelia spilota cheynei, (2)Python m. Bivittatus, & (1)Albino Python m. Bivittatus, (1)Python regius