Mom lives with me, should I count her as a dependent on my taxes?

If tax prepayer is a CPA then ask him. but, youvr going to need back up for your claim. Out of pocket
expenses. Mortgage or rent, utilities, food ect. They have to exceed Moms income.

Does she claim herself on her taxes? No. Do you provide more than half of her living expenses? Maybe. Check with an accountant or elder law attorney.