Strix's Motivations

What is your character’s greatest accomplishment?
Training herself to her current skill level.

Failure?
Secret. (Also debatable as to whether or not it could be considered a failure.)

I've just got a bunch of question marks next to those secrets
She plans on revealing it in-campaign

Fear?
Dogs. Losing friends or family.

What is the most horrifying thing your character has witnessed?
Watching a childhood friend get attacked by a dog. Or her husband’s funeral.

How did it affect them?
Left her with previously mentioned fears.

What are your character’s short-term goals?
Stopping Scarlet Circle petty crime (extortion, muggings, etc.)

I know we've already covered this, but about shorter term goals; Where is she right now? Where is she going? What does she plan on doing?
She's still living in the house that she lived in with Artyom, though she's sold almost all of the farmland.
For the first week or so before the story she's just gearing herself up both physically and mentally towards her first outing as a vigilante
She knows of a few shops that have been targets of extortion by the Circle, so she plans on casing the joints and seeing what happens

Long term?
Shutting down the Scarlet Circle, potentially fixing government corruption.

How does Strix plan to stop the Scarlet Circle, if it's a big organization she can't believe she can manage it with just vigilantism? Does she have a plan or has she just been 'winging' it?
I'd say her current plan is to find out as much information as she can about the Circle, slowly whittle away the organization, and then eventually take care of the leaders, however that may be.
Though she's starting out by just trying to stop what crime she can

How does Strix plan to avenge her husband? Shutting down the organization? Does she want revenge against the people responsible? Who is responsible?
She wants to shut down the organization and stop all government corruption - ever (starting in that nearby city). The people responsible would be almost impossible to track down.