Wow, a TAF Buttons! Your choice of pink, white and key lime sounds great to me, I'm sure it would suit her!
I've always been a fan of the 4-colour-haired ponies, so maybe I'd throw in some purple as well. Or use both pinks, Tea Rose and Bubblegum, along with the white and key lime. (opinion of a noob :-) )
I'm currently thinking of a colour scheme for TE Party Time, I got her with completely rusted tail & mane, and lots of rust inside (ewwww). I thought of combining purple, yellowy orange, green, and maybe white or turquoise, but haven't decided yet...
Anyway, I'm looking forward to see your rehaired Buttons!