How to deal with an unreasonable roommate?

Well the both of you need to talk to the other roommate. Let her know that if things do not change within a certain time frame you guys will ask her to leave. Also let her know that if she does change and starts to repeat her old pattern she will be asked to leave. By doing it this way you guys will have time to prepare for the loss of income untill you find someone else to fill her spot. There is no sense of living in an unhappy enviornment.