[Dungeoneer] Shara Quickblade's ability?

Hi there!

Today, my brother and I tried our very first hand at Dungeoneer with Vault of the Fiends. We were kind of stumped on some rules, but we did manage to figure things out with the aid of this forum and some FAQs at Boardgamegeek. One thing however still eludes me concerning Shara Quickblade's ability Assassinate:

Assassinate: pay 1 Glory to add +1 to your next Melee attack, and inflict 1 additional wound if you hit. Limit once per turn.

Is this ability usable as a response, when a monster attacks Shana, in order to pump up her counterattack?

yes, she can use it for any attack she makes.