You have the well on your own property.
The solution is only a few hundred bucks and less than half a day away.
Hire someone to install a pump exclusively for your own use.
Secure the pump such that only you can enter the pump house.
I suspect all of you are operating under an easement as a covenant to your respective property ownership.
Don't be stupid and disturb her water supply.
There are laws, criminal laws, prohibiting any tampering with water.
Install your pump, move on, don't seek revenge.
Don't get yourself arrested, sued, or become the victim of sabotage.
No tit for tat, this and that.