On the verge of capture, Vera, a peevish teenage Jew, flees the Nazi invasion of her Romanian village and crosses paths with a British secret service agent who reluctantly mentors her after she learns of her family?s murder. When her mentor is exposed as a double agent, she launches a vicious global vendetta to bring Nazi war criminals to justice before they can disappear into post-WWII hiding.

You shouldn't need to explain the need for a mentor in a logline, as mentors are archetypes often used in many genres. To that matter the presence of a mentor may work well in the story, but their mention in the logline is not necessary either.

As Nir Shelter said.? The cause-and-effect relationship?doesn't seem?strong and clear enough.? Make it personal. She may?dedicate her life to finding and?bringing to justice former Nazis, but?she's?after one Nazi in particular, the one who was responsible for the death of her family.

There was too much detail in the original logline and too few plot points mentioned.

Richiev's cut-down version is a great improvement but still lacks a cause and effect relationship between the elements and a clearly defined goal.

Considering the original post, is there one specific Nazi she is targeting in her global vendetta?? If so best to mention him or her as the one the MC is after, otherwise the story won't have an end point.

Secondly it would be best to have the target of her vendetta be the one responsible for her family's death, this way the motivating connection between the inciting incident and goal is clear.