NEIGHBOR REMOVED MY OIL TANK WITHOUT PERMISSION!

[Sol G.]

Wondering what people here would say to the following story. We have a property, and next to it is a property that is being sold. The buyers called an inspector that found an oil tank. So the buyers told the seller that she needs to remove it. They ordered a company to remove it. Meanwhile the seller went away for a month, and she gave the ok for the tank removal. they dug up took it out. When the seller came back she realized that they removed the oil tank from our property, not from her's. The oil tank from our property was cleaned like ten years ago even before we bought it and we have a certificate that everything was done correctly. The seller ( my neighbor) calls me and sends me an email that she removed our oil tank and she wants we should split the cost 50/50. Now, she went on my property (transpassing) without consent, dug it up, took out the an oil tank that was perfectly fine, filled back up the whole just with dirt and stones not even putting back concrete like it was before, and asking us to pay 50/50, which btw, she claims it cost her $12,000 and wants us to pay $6000, the price itself doesn't make sense. So I'm wondering what my friends here would say or do to such a story. Thank you P.S. I'm open to hear things that I might have missed.