You need to create a paper trail.
1) Proof of contacting the neighbor who is doing nothing.
You can have the police, a building inspector or some go with
you to the neighbor and tell her she must get it fixed now!
2) You can get an estimate from a plumbing/well contractor. If the pipe has had many leaks, it needs to be replaced. Also get an estimate to repair the damage to your yard.
3) You can protect your property either by court order or cap off the line so she will get no water. This can only be done after you put her on notice and she does nothing AND you property is at risk.
I've had a neighbor divert the natural flow of water from her back yard that ran down her driveway to the street -- instead onto my rental property. I gave her warnings. I contacted her son, a lawyer. They would do nothing. So I build a concrete wall along the property line on my side. And when it rained, all of the water from her yard went under her house, flooding her furnace and causing damage to her foundation.
That owner filed a claim with her insurance saying it was my fault. The law states here that you can not divert the natural flow of water. So when her insurance company filed a claim with my insurance company, I provided proof that I have no less than five conversations with the owner and two with her son. I sent letters, got a return receipt and a proof of mailing. I also posted a large notice on her door. So her insurance company finally denied her claim. She had to put but the natural flow of the water and do repairs to her house -- costing over $100,000.
I took maters into my own hands, a bad idea, because I had proof the neighbor was the cause of my property's garage getting flooded and she would do nothing to resolve things....
--47.156.xx.xx