If you are looking to change the person who manages your money, to pay your bills and manage investments, you should be able to go to any lawyer and have them draw up a simple power of attorney. With a power of attorney, you can control what the new person is allowed to do. You can give her blanket power to write checks, you could give her power to write checks up to a certain amount ($1,000 per day, or $1,000 per check, for example) or even restrict payees (she may not write checks to certain persons, or she may only write checks to certain places, etc).
As a CPA, this is an area where I have seen many clients confront. In fact, the American Institute of Certified Public Accountants (AICPA) has come up with a program that they call ElderCare. It is a program where a CPA can actually work as the financial manager for clients who cannot or do not want to act on their own.
If you want her to handle any tax matters, those are not usually covered by a standard Power of Attorney (POA). You would have to file a Form 2848, Power of Attorney and Declaration of Representative, to allow her to talk to the IRS, file and/or sign tax returns, cash refund checks, etc. Many states accept the Federal POA, but depending on the state, you might have to fill out a State POA as well. For example, the State of Illinois, where I practice, requires a Form IL-2848 to be filed before I can act on a client's behalf.
In summary, it should not take a lot of paperwork to have her take over as manager of your money. Any lawyer should be able to put together a simple POA that would take care of your issue easily. In drafting the POA with the lawyer, you can define what she is allowed to do, which will give you control over the matters as well.
I hope this answers your question. If you have any more, please feel free to ask and I will be happy to answer.
Have a great weekend!