1. You don't have to give her any more money. Unless your agreement was in writing, and signed, she's got nothing there. So your statement to give her cash wouldn't prevent you from selling her stuff.
2. Before you sell anything, you'd need to send her a letter, certified mail, return receipt requested stating that you are going to dispose of her belongings by a date certain. 30 or 45 days is usually considered sufficient notice. If she really cares about her stuff, she'll come get it or send someone to come get it.
Even if you give her plenty of notice, there's always the possibility that she can ignore the letter and then sue you later to get the money you received from selling her stuff, or if you give or throw it away, she could try and sue for the value of the belongings. Her success in this suit would depend on how long she waited to bring the suit (for instance, you send this letter next week and she waits 3 years to sue you), and how much money we're talking about, etc. And it would also depend on the Judge.
You are not required to store her property for her, but to protect yourself, give her a reasonable amount of time and if she does agree to let you sell her stuff, get it in writing and get an itemized list.