I would put the sewing room under lock and key and just NOT invite her into the sewing room, when she comes over, if she asks why not just tell her you're in the middle of a project (not a lie, PROJECT keep out the MOOCHER)and you don't want anything disturbed. I keep my sewing room locked, It's seperate from the main living area with it's own entrance, 2 women from my church have a key, they come to use the SPACE (ie: cutting table,design wall,etc...)not my stuff.
Good Luck & God Bless