Other person can't hear audio on FaceTime?

I was FaceTimeing my sister and she said she couldn't hear me, that my audio would cut out and then come back and repeat. I can hear her perfectly fine and the picture is good. She tried on her Mac and iPhone and they both didn't work.I'm on my iPod and I did a test on my camera and the audio was okay. I'm not covering the mic and I'm not on mute.

Added (1). I thought it was lagging too. Her Wi-Fi at school is not that good and she doesn't get good service out there.

You're internet is just slow, thats called "lag".