How to avoid spending money on unnecessary things at the mall ...

Leave it at home and only bring it with you when you've had at least 24 hours to think about it. Or immediately after she gives you the money put it into a savings account. You really have to think ahead to use that money. ... See if you could do some "pre-shopping" online and figure out what you want and how much it costs; bring only the exact amount of money you need to buy the items found online to the mall, buy them, and you won't have any money leftover to spend ...