Oh boy, I don't know if I should even put my 2 cents in. I feel your pain, I have the same problem. I don't have to worry about a "roommate" just my husband!
Our Eskimo, Waffles keeps pooping on the living room carpet & it's driving my husband Matthew insane!!!!!
I try & try though to get her to go potty outside. We have a good-sized, fenced-in backyard, so I don't see why she won't go! It is VERY frustrating & I can understand the anger. Especially is your sister is being inconsiderate about the whole situation! It doesn't sound like it's your responsibility at all & she should be the one taking care of it if she cares about the dog.
All you can do is move out when the time is right for you! I hope it doesn't break your relationship up but, she needs to be more active in caring for her animal!
I TRY believe me, I try......I hope my dog stops this nasty behavior too! I get a little defensive about Waffles too. The reason in my mind is there are so many unwanted animals that I don't want to ship her off because of this "problem." I'm just hoping that I will get her to stop & things will be "normal" again!
You can call me crazy if you want.
I just get attached easily & I'm willing to try just about anything for my husband not to kill me & the dog!!!
I hope everything works out for you!
Tina