What a sweetie! Since you mentioned Buttercup, I was thinking names of flowers...
A white flower symbolizes Innocence, Humility, Reverence, Peace, Purity, Perfection, Modesty, Virginity, Chastity, and Elegance"
How about - Peony, Zinna, Camellia, Gladiolus, Egret, Shasta, Dahlia, Gardenia, Hibiscus, Poppy, Chamomile, Delphiniums, Impatiens, Amaranth, Phlox, Cleome, Clematis, Geranium.... and the list goes on!
Obviously, a few flower names, are well... well..... a BIG mouthful to yodel across the pastures when it's feeding time, but isn't that why e have nicknames anyways?!?! LOL!