The best advise on here.
Most contractors will have public liability insurance, they would be reckless not too when there are a lot worse things that could happen than a stained drive (injuring a passing pedestrian for example). Also if he have ever had a contract with a larger contractor, they would insist on it. For minor things like this, most contractors would prefer to rectify issues themselves at their own cost mind.
I only have experience from a contractors perspective when issues occur from defects in subcontractors work. In this case there is always a contract in place and we are usually using them on other contracts or ongoing work. In these cases there is a defects liability period of 12 months where any issue arises the subcontractors have the opportunity to put if right themselves. If they refuse or don't do it in a given time period in line with what the above poster said, we then carry out the rectification ourselves or get another subcontractor to do it and contra charge them. A lot easier in our case where we have payments for other work to take it out of.
They still have liability for their defects outside of this initial period, but they lose the automatic right to do it themselves, we could pay someone else to do it then try and claim from them but in most cases the cost isn't worth it for minor things, so if there is no ongoing relationship we often just swallow the cost. But as a larger company with our client relationship the most important thing, we just get it done swiftly to keep them happy. This has included times where a subcontractor was no longer trading and their work had damaged a neighbouring property. Understandably as an individual who has hired a professional to carry out the work, you don't want to swallow the cost yourself.
Just follow the steps of the previous poster, that is the best course of action. Your only issue would be if he had ceased trading. If you don't want to go though all the hassle then just offer up the staining yourself. It's good stuff and will look like new if you ignore her holes. If you make the offer though, is there anyway you can do it so you have evidence by messages or emails?
All the other posters thinking you should just pay out 10k for a new drive when the colour is the issue, not the structure 😂 like they would fork that out if they were in the same boat. Who just had 10k sitting in the bank anyway. You should have pushed the contractor to do this straight away, but NDN taking the piss thinking she can get a new drive out of this. If he dropped something on it and took a chunk out, that would only make him liable for a patch repair. Seems like the only reason she is pushing it further now is because her drive has worn further and she knows she needs a new drive and you are her best bet.