Well unless she wants to give up the larger room.... NOPE.

I understand not being able to kick your sister out. But a serious talk about when she is moving out, and that she can't just keep flip flopping on it is needed. You are going to have to plan around that financially and need a concrete date. That is not too much to ask.

Can you again sit down with her and try to calmly work out a cleaning schedual. I know you have already gone over this with her but having 6 bags of garbage laying around the hall makes it obious that she didn't take it out like she said she would.. cause it's still there.

Kids can be messy so sure you might have to do more of the cleaning but she can do somethings to help out. How you get her too, no idea. You could tell her if she does not help clean that her rent will include a cleaning service fee. It's not a hotel and you are not her housekeeper or mother. Or if she is really going to move out than you might want to just try and put up with it till then if you can, for sanity sake.

Sorry you are in this situation. She doesn't have children so she likely really has not thought about what it is like. Hard to get the real picture until you become a parent.