Or start looking for a new roommate..

You supplied food, thereby raising your status in the pack. Feeling threatened, your alpha roommate has merely expressed her wish to reacertain her dominance by marking her territory- which includes you and all of your possessions. I suggest you puff yourself up as much as possible and maintain silent, steady eye contact with her. She may be stronger than you now, but if you seem threatening enough she won't want to fight you. Then, and only then, will you be able to live peacefully beside her within the confines of your lands.