How Long Can A Puppy / Kitten Absorb The Antibodies From Colostrum??

I have a little girl and we’ve been taking her to the vet every other day for 2 weeks. She’s still not eating anything but mushy food, so I’m wondering if she’s getting enough antibodies from colostrum? Or is it too soon to take her back there again?? The doc said that all babies need their ‘approval’ before they can be put on formula…I was told since she isn’t eating well its best to wait and see what happens with the next feeding. Thanks!