Does Durable Power of Attorney give me the right to take away my mother's check book and not allow her to write checks anymore from her account?

No, You would have to have her declared legally incompetent, then the court will appoint her a custodian.
Could you convince her to let you manage her money so she doesn't have to worry about it any more. My brother and I sat my mother down and explained that she could not manage a check book anymore and that I would pay her bills for her (I have POA) and give her spending cash. At first she kept saying she didn't understand, I ended up pulling out her register and showing her where she had done things she shouldn't have She kept saying I don't remember doing that and I told her I know that's the problem, you don't remember, it's not your fault, let me take care of it and she did. Good Luck!