After a land survey reveals that her fence is in the wrong place, a homeowner, unwilling to lose part of her backyard, wages war against her neighbor ? no matter what the law says.

I see the problem here. Maybe there should not be proof of law, and the act could have gone on unapproved at the time. That would give her two reasons to fight.
How about:
A generous neighbor replaces a downed fence when a homeowner is gone, but instead of following the original fence line, he angles the new fence line to go around a tree, thus stealing inches of property from the homeowner - inches she wants back. A war is waged and the whole neighborhood will pay.

Shouldn't the neighbor be the protagonist and our POV? And why is she so motivated and inflexible (and wrong) about this stolen hunk of ground? Are her beloved cat and family jewels buried there?

Thank you. I need to revisit the motivation.