How do you unpair a watch without the iPhone or passcode?

I received an Apple Watch Series 7 as a gift. It is still paired to the previous owner. She told me that she unpaired it from her iPhone so that I could pair it to mine. After three separate attempts I’m still unable to pair it to my phone as the error message tells me that it’s still paired to another phone. I do not have her passcode. How do I reset the watch?