Help with ex-landlord? Legal advice?

You made a verbal agreement with her which is a contract. My suggestion is to scare her with a small claims court summons or a tenancy group, if you have a tenant's rights association go talk to them and see what your rights are. Contracts are legal and binding, but if agreements were made in "bad faith" a contract can be broken. Inform yourself through your provinces laws and then write her a letter, stating the overcharging and 'bad faith." You do have something valid with which to contest the verbal agreement you made with her. It's likely that because this has been done illegally, she will back off and do nothing.