Dear Ms. Demeanor,
My roommate just brought home a rescue dog. It is kinda cute, pretty smelly, and has taken over our minuscule apartment (a one-bedroom converted to a 2).
I have told my roommate that I will not participate or contribute in any way towards the care of this dog. I also think my roommate should start paying more of the rent since she is effectively adding another being to her 'share' of the apartment, making my share (and kitchen cupboard space) smaller.
If your roommate brought home a dog without consulting you first, you have more problems in your relationship than who pays how much rent. This is a huge imposition she has just heaped on you without consideration for your feelings, concerns, and possibly health. (What if you were allergic to dogs?)
You can draw all the lines you want, but some of the care of that pup is going to fall to you. If you get home first and the dog needs a walk are you just going to ignore it and let it do its business on the floor? Doubtful.
You need to sit down and have a serious discussion with your roommate, possibly giving the dog (and your roommate) a trial period before making a final decision. I do not know the terms of your living arrangement but, if the situation is untenable, it may mean either you or the roomie becomes the stray who needs rescuing.
Ms. Demeanor is channeled by a longtime Manhattan vertical dweller and real-estate voyeur who writes under the pen name Jamie Lauren Sutton. She is here to commiserate, calm and correct. Please email your quandaries to firstname.lastname@example.org and put "Dear Ms. Demeanor" in the subject line.