Advice?

I don’t post on Reddit but this has been bothering me. I’m a minor so I’m under my parent’s rules obviously. And I’m aware on how much bedding my Syrian needs. My mom says he doesn’t need that much and that it’s a waste of money even though she agreed we would put more in, I guess she changed her mind.

Any advice would be helpful on how to convince her to care for my hamster! <3