Is there any special paperwork I need to be able to do if my friend wanted me to do her taxes, manage her bank account and pay her bills?

You should go to the IRS site (www.irs.gov) and look for the Power of Attorney Form. You need to have your friend who asked you to do the taxes fill this out with the tax year(s) to which the power applies and the Forms you will be filing. This needs to be signed by your friend and you and filed with the IRS.

Yes, you will need special paperwork to do these things. In order to prepare and file her taxes, you will need to be certified by the IRS as a tax return preparer. In order to handle her banking, you will need to find out from the bank what kind of written permission they want her to sign. As far as paying bills is concerned, if you are going to pay those on line, then your friend needs to give you written permission and access to her on line bill paying account. If you are going to write checks on her checking account, then you need to be added to the account as someone authorized to sign checks.

Probably you should have a carefully drafted power of attorney. As for her tax returns, once they are prepared, you could email them to her to print out and mail to IRS. Assuming she is abroad on April 15, she will have an automatic 2-months extra to file.