Tenant moving out, how to split bills?

[Josh W]

A friend of mine, E, owns a house that she doesn't live in. She has two roomates, V and P.

P has lived with E for a long time. While living with E, they had a couple of mice, cockroaches, and a bunch of yellowjackets outside. P begged E to pay for pest control. E could not afford it, so P agreed to be "financially responsible for it" (P's words...nothing written).

The contract for the pest control is a year contract. E has now moved out and is just renting out her house. The contract goes on for 10 more months. P just moved out.

E and P are friends, so going to court or anything like that is silly. Nothing is written, just verbally agreed upon. P thinks "now that I'm not living there, I don't need to be 'financially responsible for it".

Who should pay?

50/50?
P should pay?
E should pay?