Food Transition

Janey-Doe was spayed at 4 months old. She's now 7 months.

My vet told me to feed her the regular FF Kitten up to her 1-year birthday, and then gradually transition her onto FF Adult. The FF Kitten has all of the nutrients needed for her growth. According to the vet, I can feed her half a can of each (half Kitten & half Adult) up to 18-months of age, after which I continue with the regular Adult Fancy Feast. Makes sense enough to me.

It doesn't really matter. "Kitten" food really doesn't contain anything special other than often times it's higher in calories because kittens have higher caloric needs. You could easily just feed her "adult" food if that's what she prefers, as long as she gets as much as she wants she should be fine. I would encourage you to feed a canned food rotation tho and not just rely on fancy feast. Although its' a decent low cost food she'll benefit from both a brand and protein rotation in her diet. 

Is she a "large breed" kitten?  Reason I ask is MY Vet said it's ok to start feeding them adult food at around 8 months.  No need to even do 50/50.  But normal size cats reach adulthood at around 12 months...some large breed cats take much longer and therefore I guess I can see why a Vet might say to keep them on some kitten food for longer

I agree with missmimz though in that I would begin to add in additional brands as you transition her.  Otherwise she may become a picky eater.  If FF ever has a recall, you be up a creek.  I keep FF CLASSICS in my rotation, along with other brands, just to be safe.