A World War II British Army nurse gives up non-combatant status to sabotage her German captors’ ambush of a British patrol, which leads her towards overcoming fears, superstitions & desire for safety in her increasingly dangerous world.

Agree with Richiev.

There's a lot of information in here that isn't necessary to a logline and you're missing some that is. I've gotta ask as well... if she's been captured, how is she going to be able to do much at all?

Everything after "patrol" is unnecessary in a logline - she's a nurse on the continent during WWII... the world is about as dangerous as it gets so her desire for safety and her fears are all pretty much a given. What we do need though is a more visual description of what she's actually going to do and how. Tell us more about her too. Give her a characteristic that suggests her emotional journey.

Hope this helps.

"When she discovers a Nazi plot to ambush her brother's British unit, a captured nurse must..." (Then tell us specifically what she must do: Must she destroy a bridge? Must she seduce a Nazi officer? Must she poison the Nazi food? What must she do in order to successfully stop the attack on the patrol?)