I don’t know all the particulars, but I wouldn’t sit back & let things happen, get ahead of the crazy neighbor.

1st off, mind your P&Q’s with the property line, then start a paper trail on her shenanigans and threats. I’ve known people to set up surveillance cameras on the property line. If she shows up for the fight with a knife, you take a bazooka(figuratively speaking of course).

As a friend often says, ‘two can play that game’.