Female roommate!

We've never got along - my fault though - I've let my roommate flip out on me while she was there once. I didn't put him back in his place, which i should have, but bygones be bygones, she now assumes she can do what he does.

Situation: Lights were on in my room.

Her: yo godmodus, your lights are on, can i turn them off or are you going to flip out again if i do?

(she did once before, and i did, basically falling for her shit test)

Me: I'll come home and turn them off, thanks for offering though.

I come back home, (i was nearby, 3 minutes away, these two messages were less than 30 seconds apart)

the light was off, the door was open. It continues:

Me: I'll turn off my lights next time, especially when i say i will :) thanks! Me: And if i do forget, just let it be.

Her: Oh i was already gone, sorry! but i find that it was unnecessary to leave a light on when no one's there.

Me: I said no. and i won't "flip out", but don't do things that invade on my privacy, no matter the reason. If i leave a light on, i'll pay the dollar it costs.

Her: I'm just saying it's pretty anti social towards us if you waste energy! it effects us all (she means humans) when you leave your light on godmodus!

Me: you don't seem to understand.

Me: I said don't, and you did it. no permission -> don't do it.

Me: Now i'll let this go for the sake of the peace, but do avoid doing things like that in the future.

Her: You answered only after i have left! and you don't seem to understand that there's no reason to keep the lights on!

Me: Right, beyound what just happened, you did do a good thing, the world thanks you. But like i said, a no is no.

Her: beyound that, screw you godmodus.

Me: we'll talk again when you calm down

Her: Won't happen!

That was it, now we'll probably meet again soon. She'll be her usual passive aggressive self. What does TRP recommend be done? Personally i'm thinking of going the nuclear option, but for the sake of my other roommate, I am considering other options.

edit: i understand the downvotes. this is no pleasant situation. i am relatively new, and am here for advice. i wouldn't classify myself as beta, but i come from a house in which these sorts of things would not happen and it's hitting me where it hurts.