Does a defy that does nothing because of empowered blue Mel still count for abandon hall?

Yes. Defy resolves normally (it isn't itself countered), so it counts as a played spell for Abandoned Hall even though its counter instruction did nothing.

Mel, Newly Awakened's Empowered ability ("Your spells and abilities can't be countered") only stops the counter from succeeding — Defy's instruction is simply ignored on resolution. A spell that resolves with no effect is still considered played (Rule 359.3.e.10). The "not considered played" rule (425.1.b) applies only to spells that are actually countered, which isn't the case here. So once Defy finishes resolving, Abandoned Hall's "when a player plays a spell" trigger fires, and the Defy's controller may give one of their units there +1.