[Gracie2006]

It might be that Bella is telling your nephew that the space she is in is HERS and she is protecting it, as one of the leaders of HER pack. Hopefully, you and your husband have established yourselves as pack leader with Bella, and as such, she is calm submissive around you. However, your nephew is a new person that has not yet established himself as a leader in her eyes. Gosh, I have been watching the dog whisperer too much! Anyway, can you try some activities with your nephew to help establish his ranking in the pack? Things like going on a walk with you and Bella, he holds the leash and keeps Bella a bit behind him. When going out of the house, have nephew go out before Bella. Have nephew feed Bella, but only give her the food after she performs a command like sit, or down. Teach him some of the disciplinary things that you do with Bella so that he is consistent when he is around her. You will need to work with him and supervise him. Just some thoughts. If those don't work, you might consider hiring a behavioral specialsit to help you?