My daughter can't facetime me on my iPhone 4 using her 4th gen iPod. Can someone help me?

My daughter has an iPod 4th Gen and I have an iPhone 4. She can facetime everyone but me. When she and I try to facetime, we get a pop up that says "Facetime Failed" - Mom is not available for FaceTime.

She is a minor, so she shares my Apple ID with me. She can iMessage me, but Facetime will not work between us two. What are we doing wrong?