This is your house. If you're not comfortable with what's going on there, then that's not cool - you need to be able to relax in your own home! Your husband may be okay with what's going on, but if you're not, then he should respect your feelings.
As ugly and hard as it may be, it is time to take a stand for yourself. I think you need to talk to your sister calmly and directly. Maybe go to a neutral location - coffee shop or restaurant - to talk if you're afraid she'll blow up if you talk in the home?