Respite/Family conflicts

My sister, who lives nearby, and I take care of my Dad who lives in our home. We gave him our first floor bedroom (in wheelchair 95% of the time) and we moved upstairs. She's over here a lot, to relieve me mostly midday and evenings if my husband and I go out. I have asked her NOT to go upstairs as that is OUR space, since the first floor has been invaded by my dad's stuff, nurse's visits, PT, etc. We very much need a space that is Dad-free and where we can go to unwind. My hubby and I want to go away and my sis has agreed to stay here as she has done before and those shorter times she slept on the first floor living room couch. Now she says she wants to sleep upstairs in the spare bedroom next to my office with all my stuff in it, and my bathroom is off the spare bedroom, with all my stuff. I feel this is an invasion of my privacy (and I hate myself for not feeling more open) but she feels she'll be too uncomfortable on the couch for 10 days. Am I wrong not to let her stay upstairs? Alternatives would be for her to go home at night after she's put him to bed (he never needs help during the night); hire a caregiver (she says why do that and spend the money when she can do it); just say no and have her sleep on the couch, unhappily. Best scenario would be to get a single bed and set it up in living room of first floor (problem is storage of it when not in use). Any thoughts or ideas? I told her I would think about it but I really don't want her upstairs. Thanks. Sasha