I'm not sure if this is an editing error but

The part after Amy falls through the ice and they are all sitting around her on her bed, Amy asks Jo "Jo do you love Laurie more than you love me?" and Jo says "oh Amy, don't be such a beetle" and a few seconds after you hear a voice say "beetle?!". No ones lips move, it doesn't sound like any of the girls and it sounds out of place. I'm wondering if it was an editing snafu. Just something I always pick up on when I watch it!