I really hate to tell you this, but when you trade a Pokemon to a different cart, the friendship resets (because it has a "new" trainer). :X
The best thing to do would be to just make the Eevee hold the Soothe Bell, place it first in your party, and then ride your Mach Bike up and down Rustboro City or some other big straitaway for about ten minutes or so, then go back to Verdanturf Town to check its friendship, then repeating until it loves you enough to evolve.
EDIT: If you give it Proteins, you'll mess up its EVs horribly. You don't want an Espeon with a bunch of ATTACK EVs. ._.