You guys should switch jobs

Don't do her tasks then, and let her incompetence be shown.

Why are you doing the tasks for her? Wouldn't you have a better chance of getting the position if you stopped making it seem like she knows what she's doing?

I wouldn't have done her work for her. If they didn't hire you, let them find out the mistake they made with this incompetent fool.

This is a good example as to why seniority doesn't always mean "qualified"

And the one who interviewed you is too stupid for his/her position.

Don't do her job. She's being paid for it-you're not and if she can't do it, they'll soon find out. If you do it, she'll get all the credit.

Welcome to the struggle

To play devils advocate, depending on how long she has been in the position, there is a learning curve for most people. In my position, I needed a LOT of help learning my position when I got it. There was SO much to learn- behavior plans, and goals, and meetings, not to mention learning about the girls I work with, and their parents, learning my staff and what leadership style they each needed. I am sure someone thought, great- they hired some girl fresh out of college who has no idea what she is doing. Give her time. If she is still having issues, then speak to her boss. It may not be the position for her.

Maybe go and show her how to do it