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.

Thank you so much. This helps.

The concept would improve if this "...unwilling to lose part of her backyard..." would be changed for a compelling reason for her to need to hold on to all her land.

What if she discovered a gold ore vein or oil deposit in her backyard? Or what if her beloved husband or child were berried in the backyard?

I think the motivation is weak and needs to be cleared up for the audience to want to see her achieve her goal.

Hope this helps.

Drama won't work, because it is too mundane, imo.
It could be a funny comedy if it slowly escalates to outrageous proportions.
But that would be a TOTALLY different direction from where I think you want to go.

It seems natural for a comedy, because http://tvtropes.org/pmwiki/pmwiki.php/Main/PropertyLine

Your soccer mom/crime boss idea is very funny!

Seems like a natural for a comedy, a dark one perhaps, but still a comedy of human folly.