It can be really inconvenient to date when you have roommates. Your roommates might get annoyed that your partner is sleeping over most nights of the week, using up all of the water, and sitting on the communal couch all the time. On the flip side, you might get annoyed that your roommate's partner is taking over your life. You overhear them up to no good every night, and while you're happy they're having a good time, you also want some shuteye! Some people will specifically request single roommates because they hate it when people's partners come over. Others will specifically refrain from dating people with roommates because they don't want to deal with the drama, which is a totally understandable stance, especially when you're in your 30s and tired of roommate debates.
As far as I'm concerned, I'm all good with my roommates dating and bringing dates over, as long as their boyfriend or girlfriend eventually goes home. I am not cool with adding an extra roommate to the house full-time, unless they're going to pay their share of the rent. If another roommate means that I have to pay $400 less in rent, then I'll definitely consider it, but I cannot deal with my roommate's partner mooching off the rest of the household for months and months on end. That is what happened to the girl in this story, and I do not want her life.