I would very carefully box up anything that's been left behind & store it properly.
Write to her & let her know you're going to keep the stuff for a specific period (say three to six months) then send the letter by registered post so that she has to sign for it & you'll have proof she received it. Then a week before the end of the time period, write to her again to let her know you'll be getting rid of the stuff, again send the letter by registered post.