Just a reminder, if you do that, the storage place has a contract with YOU, not with the person whose stuff you are putting there. If they don't pay up, sure, the storage place can get rid of it (eventually) but in the meantime the storage company can come after YOU for the fees, possibly resulting in a civil judgment and/or a ding to your credit.
I'd ask a lawyer for advice. I suspect you are free to get rid of whatever you don't want to keep after giving her reasonable opportunity to move it. This reluctance to be the "bad guy" is keeping you stuck doing all KINDS of things you no longer have any obligation to do just for the sake of trying to make happy a bunch of people who will continue to take advantage of you.
Backbone time!