dose blue mels empowerd ability give ahri legend -1 might more when it is activated

No. Mel, Newly Awakened's Empowered ability doesn't add an extra −1 to the Ahri legend's ability.

Mel's Empowered text only boosts "a spell or ability you control that gives −[M] to a unit it chooses" (replacement effect, official FAQ #11737). Two reasons it never touches Ahri's legend: (1) the Ahri legend belongs to a different player in the typical "they attack into you" scenario, so it's not an ability Mel's controller controls; and (2) even if one player controlled both, Nine-Tailed Fox doesn't "choose" or target a unit — it just gives −1 to the attacker referenced by its trigger (per FAQ #6019, it doesn't even trigger Deflect). Ahri's trigger resolves at a plain −1, min 1.