She is protecting you at the obedience classes, at daycare you leave right? so she can play w/out having to think about protecting her precious owner. She probably is ok before class but then she knows she is being taught something & protecting mom is her best trick
You may see if the teacher will handle her during class to test the theory & then see what you can do to work on her protectiveness of you. My girl bites my husbands hands when he touches me, just that little pinching/warning bites-but they still hurt. She is she tiniest sweetest little thing ever until someone messes w/her momma -then its on. I picked up my friends dog & she charged & snapped, didnt want mom holding another dog, I corrected her & she ran, hid & cried real tears, I love that she loves me so much but I know the behavior isnt healthy for long term because one bad behavior breeds another & another...I am working on correcting her. I could be wrong, but something to think about.