I used to do this with my mom. The caveat was that she actually paid me back when she got her paycheck a week later. And I still got a new account for my bank deposits at 21. Kept the old one open with 50 bucks just in case for a while and then closed it. She needed 20 dollars here and there but tapered off long term. She's never needed money since.

That easy access is a life vest as much as it probably encourages unwise spending. They know they don't have to be as careful cuz you're there, but if you didn't exist they'd figure something out right?