i posted asking about that in gamefaqs too,but friendship is pokemon amie not hapiness,at least that's what they said.
Maybe this....
Via gamefaqs: Equip it with Soothe Bell if you have it. Put it in the front of the party. Let it level up. Don't let it faint. Give them vitamins, healing items, and various others. Run around a lot. (you already did these things).
Same goes for every Pokemon that evolves via happiness.