Variety is the spice of life. You get to work with coffee and then you get to do other things too.
Once upon a time, many years ago, I worked at Target helping to set up a new store. During those few months, I never had a problem deciding what to wear to work. I still have some of my red shirts and kacki slacks.
Do you have a place outside where you can roast your coffee?
Does the smell of your sisters "apple, cinnamon, vanilla, whatever candles bother you? I think a compromise is in the future. But if it's her house, then she wins!