What do you mean by can't handle it? One thing we want to do as a caregiver to our LO with dementia is to keep them involved as long as possible. Allow her to feel important. You've got some good ideas from below. Let her fill out a check, you just don't mail that one.
You've not given us much to go on, but if she wants to be involved in her finances, have her sit next to her when you are paying her bills either online, or by check, so she can at least feel like she's involved. You can also show her any bank statements, and explain them to her(even if she doesn't understand), as it will at least make her feel like she is still somewhat involved. Sometimes it's the little things that will keep peace in the home. Best wishes.
Give her copies of bills and let her write on the calendar when they are due?
Gave her fake cheques to fill out.