set the fire on fire

said to a person who is doing more harm than good but because you're already in such a horrifying situation, which you think couldn't get worse, that it doesn't matter as this person's efforts are pointless and wouldn't make any difference.

A: I can't believe that you two broke up.

B: he learned what have I been doing... Jes is going to tell him that I cheated on him with john. She's just setting the fire on fire I've told so many lies , another one won't hurt

(imagine two criminals that are stuck in a room and if they can't manage to get out they'll die. there's only a desk and an old phone in this room and the police is already after them)
A: what are doing?!
B:I'm calling the police
A:what?! whatever, set the fire on fire we're going to die anyway/ we're gonna get arrested anyway