A lot of confusion over this. Long story short, you should call VZW before turning the phone on and maybe by now the reps know what's going on and how to do this but most likely no matter if it's activated on your mom's line first or moved right over to you then you will need to wait up to 24 hours for the phone to activate on your line.
If a VZW rep tells you that a new SIM is needed or it needs to be swapped, don't believe that. Everything can be done without going into a store or swapping SIM. it might take 24 hours to complete is really the only issue to know.
I called right now to ask so tomarrow when i get it im more of what i can do but they said if i call when i get it tomarrow they can swap it right onto my line? which i questioned wouldnt i have to activate it on my moms line first and they sad no itl void or something? hoping it works out they way the guy told me as simple as he said it.