Being from the Deep South, I understand totally how hard it is to be rude to someone, even when you really want to. The hardest thing to deal with is someone who acts like everyone owes them something. The Poor, pitiful, lucky you syndrome.
I have found that, when it comes to my stash, I may not know what I want to do with it, but I don't want to share it, & I really don't want anyone going through it looking at it to try to find something they want. I figured out that if I just don't go in the sewing room when they are in my house, I don't have a problem. I do have a lock on the door & keep it locked unless I am sewing. I give when I choose to, not when I am pushed to.
Ideas...suggest things that don't cost...take a walk, weed a flower bed, make some tea, sort your clothes for laundry. lol Really boring...watch something on TV that she hates or worse, hand her a dusting cloth & let her help you clean house. Best of luck with your problem & with your move. I hope you get good neighbors!