Don't know where you live so I'm not sure if freezing is an issue in the winter. Also remember with a pump when you have elevation rise you loose pumping GPM with rise. So if you get 100' of rise to the pond a 10GPM pump won't be 10 going uphill.
You have to get some professional opinions on this situation. Call the town or county in the case you and the neighbor can't come to an understanding. I'm thinking worst case scenario on your part.
If gravity is an option my vote is for a drain to the creek. The cost of pumps, electricity, hassle isn't worth it. A small ditch to the creek will keep water in a small confined area for both of you and allow you to go about your life not worrying about power outages, utility bills and the like