Flashing Blade + Mjolnir

Actually... I dunno? I don't think so.

"If using another similar skill, only highest value applied" This is from Flashing Blade, so it might not.

Mjolnir reduces your cooldown by 1, whereas flashing blade gives you more cooldown charges. They do different things, so the effects are not in conflict and therefore they stack.

Mjölnir reduces the Cooldown Count, while Flashing Blade increases the Cooldown Charge. Those are two different things. Flashing Blade doesn‘t stack with skills like Steady Breath and Bold Fighter. I also wouldn‘t run Flashing Blade on her. Instead I‘d keep Swift Sparrow and give her the Heavy Blade sacred seal.