I think Lindy's biggest issue is that she's a bit too black and white when it comes to justice. The reasons don't mean as much as the fact the crime is being committed: She wants to stop crime, not take time to pity someone. Krav Maga is also one of the most brutal and to the point arts there is; You're instructed to take down your opponent at all cost to protect yourself or your family: I think this brutality might lead Lindy into doing something she'll regret: Either caused FROM trying to protect someone, or just not knowing her own strength well enough to not slip up and deliver a fatal blow.
Such a thing would be extremely devastating for her. Not quite sure if she'd cope in any reasonable manner, honestly.
I don't think any sort of villainous turn is possible for the character, but I do think that her perspective of justice can definitely change based on what real-world experience she receives. And with a change of perspective, comes a change of action.