geniune options. telling people they just have to do something ignores whatever reason they may have for not doing it. trying to figure out why they do things how they do it and working with that, not against it is a good idea. Its easier to recycle if people can put their recycling out with their trash, it's easier to eat organic if you can find organic food in the supermarket, it's easier to vote if you can get an absentee ballot mailed to you. Die hard voters and vegetarians and recyclers will do these things anyhow, but to get reluctant people to try new things, if the moral argument isn't working, you'll need to take another tack.
compromise. just saying "because I'm the mom, that's why" generally flies with no one, even the kid. Figure out what you could do differently to achieve desired results and make an offer.
sanctions. Though I'm not in favor of some of the "dishes in the bed" techniques mentioned here, they do get results. Figuring out what is a real deterrent [hint: it's not you asking nicely, or hollering, apparently] to the bad behavior can be a start. In this case, vermin is really a dealbreaker. If the roomate wants to put all her dishes in a plastic bag to keep it free from vermin, that's maybe an acceptable compromise, but make it clear, she has to deal with the vermin or you both get evicted, leading to #4
solutions. often ideas that come from the person being forced to change willl have more long-lasting appeal. Ask her what will work and then work on some way to enforce whatever deal you guys agree to. stick to your part, have her stick to hers or come up with a working solution
crossing the line. and, at the end of it, she may not ever tow the line. be prepared to either move out, make her move out, or live with it. Ultimately, you can't make people do what they won't do, but you can choose what you do [and no I'm not in AA but this has always struck a chord with me]
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