I have name-changed for this, because, well, you guys can be scary!
Sorry if it's a bit long, trying not to drip feed 
So, the story is that a couple of Saturdays ago I went up to the local park with the dc and ddog. DC took their bikes, I took a ball to throw for ddog. We live in a small village and we were the only ones on the whole park.
Ddog, has a number of doggy friends and is generally friendly with other dogs; however on a few occasions he's growled and snapped at unfamiliar dogs we've come across on walks and so I always put him on the lead the second I see another dog approach.
We'd been there for a few minutes, when just as I'd thrown the ball for ddog, ds fell off his bike, grazing his hands and knees and I rushed over to him to mop up the blood! Just as this was going on, a woman and her dog arrived at the park and before I knew what was happening, ddog and the other dog were fighting. I rushed over, dragged ddog off, took him away and tied him up so I could go back and see how the other dog was doing. He seemed OK, but I apologised profusely and told her that although he seemed OK, if he did need to go to a vet, then to let me know. The woman was very understanding and nice about the whole thing - I felt awful, and cross with myself for being distracted at the wrong moment!
A couple of hours later she turned up on my door and told me that she had decided to go to the vet because the dog and been limping, that he'd had a couple of injections etc and would be going back the next week. I told her to let me know how much it cost, and she told me that she was insured and was happy to claim if the bill went above £75, which was the standard excess. I told her that I would of course pay the excess and we parted on good terms.
A few days ago she came round to see me again, with a bill for £145 and saying that actually, she didn't really want to claim on her insurance so would I please either claim on my insurance or pay the whole thing. Our excess for third party claims is £250, so no point in us claiming and I agreed that I would pay the £145.
DH, however, is not happy. He says that it's unreasonable for her not to claim on her insurance as a) that's what insurance is for b) that's what we'd initially agreed and c) there was nothing to stop her from claiming from her insurance in addition to us paying her the money.
So, who's being unreasonable, me or dh? What would other people do in the same situation?