My pitbull is a new mother and she wants to kill my new 2 mth old puppy i just came back with?

my pit is a black stiped pure american pitbull she just had a litter of 8 , 3 week old pupps and i just got this little house fluffy kinda pomeranian like weird mix but its tiny and fluffy and shes like 2-3 month old and she loves my german shepherd and the love is likewise but she tried to be freinds with my pit and she almost bit her head off .my pit is a yard dog and the little dog sleeps in the house my pit went all the way to the 2nd floor just to look for her (wich she ever does cuz shes scared of the stairs) so im afraid even after her puppies are grown up she still wants to kill it WHAT SHOULD I DO