Repair advice / neighbor advice

The neighbor that shares my back fence came to my door last night to inform me she's having the fence replaced and was quoted $2k. She said it would be good if i could pitch in on the cost. Although I want to be a good neighbor and share the cost, I'm frustrated that I had no say in any of this process. My frustration makes me not want to pay.

I purchased the house this year, and the fence was leaning before I came into the picture.

She has big dogs and doesn't want them to get out through the fence and do harm. I have no outside pets.

What would you do in this situation? I haven't seen the completed fence yet, it's supposedly happening today while I'm at work.