It's not trivial if it affects property values.
IMO I'd side with her as I think well manicured lawns uniformly stamped out are boring and a little bit cultist. Just look at many home owner's associations. So many rules and so little freedom. This is a similar situation even without any association calling the shots.
As far as the garden thing it reminds me of the trees everyone has in the patch of lawn closest to the road. Those are technically the cities trees and they own them thus you aren't allowed to remove them etc....
Also sidewalks iirc. If they need to be worked on, the home owner has to pay. However it's considered public property therefore if it snows and children and other people can't walk on it safely then you're to blame.
It's a balancing act and the laws don't always provide logical reasoning. On one had if everything were made public there would be no ownership of anything and no one would pay for anything to be fixed....they didn't screw it up or only did a small part why should they pay the most? If everything is private you can turn your own yard into a junk yard and sell car parts with 12 pit pulls running around. After all it's you're fucking land right?
There needs to be a system to weed out cases like this that really aren't problematic. Let the block decide perhaps; let them vote on it sorta like if a block of people want to have a block party. You can have the road closed etc...as long as everyone agrees.