the caveat to the previous post about turtles being "easy" is that they are ONLY easy if you spend a fortune getting the right equipment to set up an extremely large tank right away, cycle the filters properly, and get a biologically sound tank running before you even consider buying the turtle. You can spend several hundred bucks doing this, all for a $5 turtle.
If you do not do this, maintaining your turtle will be a HUGE pain in the booty, requiring constant water changes and filter cleanings on small tanks with cruddy filters, the turtle will be less likely to stay healthy, creating vet costs, etc.
So you can go cheap and extremely annoying, or you can go expensive and easy....
But if you can't keep animals alive in the house, your mother may have a good point. A hamster costs relatively little to set up and care for, a turtle can cost you a fortune. If it's not alive long, for whatever reason, you are still out a few hundred bucks for the setup.