Glad to hear the bad neighbor is moving out....
Those types generally create chaos in all areas of their lives, she probably had issues going on with everyone she came in contact with...
Personally...
I disbelieve that the neighbor is responsible for the butterfly bush...
And...
Those buddleia are documented invasives up in your area of the country.... probably for the best to plant something else...
I've found that in the deep south, they are prone to root knot nematodes...
so... I plant vitex instead.... Very drought hardy, and a host plant to the rustic sphinx... as well as attracting butterflies and hummingbirds!
Here's hoping the next neighbor will be reasonable...
I like the idea of tilling up that troublesome foot of turf... after digging it out and discarding...
And then sow annuals....
Cleome are good pollinator-friendly plants that will not need a drop of extra water...
Anything we can do to reduce the turf grown in our yards, and increase the pollinators.... is a good idea, and every neighborhood hoa should require it done!