Arkham Horror
Can Marie use Witch Blood while engaged with a monster, or repeat an attack on the same monster?
No. Witch Blood is an action, and while engaged you can only attack, evade, focus or take actions that say they work while engaged. So Marie can repeat an attack on the same monster only if it is exhausted or otherwise not engaged with her. The same limit applies to an investigator given Witch Blood via Smoky Velvet.