Aggressive Neighbour

Its a difficult one, but I'd certainly stop her borrowing your land again.

Are there any local bylaws about lighting fires etc? It may be worth checking these out.

Ignore the woman and tell your DiL to carry on with her training. I don't believe it upsets the horses at all. Tell your DiL to put music headphones on then she won't hear her.

Perhaps writing a letter to her but not posting it might make you feel better. Make a bonfire and throw the letter on it.

She certainly would never be borrowing any of my fields for her horses in future, that's for sure.

Are there any local bylaws about lighting fires etc? It may be worth checking these out.

Oops, X post, yes, check this out first!

Would you consider walking the dog while your DiL runs. If the neighbour pops from a hedge to dictate you can put her straight. I would very firmly remind her it is your land she will not have access to it in future. Keep it short and walk away you have every right to deny access.

I wouldn't send her a letter. Like someone else said, write one then burn it. But never give her your field to use again.

I wonder if she was worried that the dog could go near her horses?
However, there was no need for her aggressive attitude

I would definitely stop her using your land, if she ask why she can't you can say your family will be using regularly and you don't want her horses being frightened , I am sure she is very thick skinned so having a word with her would be no good anyway. Just one other thing did she know it was a relative of yours or just a random person out running if the latter perhaps it was just concern for her animals.

I'd tell your neighbour that it is your daughter in law, in case she wasn't sure who it was. Tell her she will be training round your field frequently until the marathon.
Don't send a letter, these things can get blown out of all proportion.

agree with your husband.
don't write anything.
if ever you wanted to sell, you would have to declare a neighbour dispute.
if she asks to use the field, say no, not available, being used by family for marathon training.
and walk away.
less said the better.

I have horses: for many years now they've been "field ornaments" as I'm not fit to ride any more. However they are not stupid - horses aren't, in general - and although a horse is often likely to spook at silly harmless things due to being a prey animal, if it's regularly handled as it should be, a person and dog running in a completely different field behind a hedge is defo NOT going to faze them one teeny tiny bit.

I wouldn't say a word to your neighbour until either your DIL comes over again, in which case pre-warn neighbour that she and the dog will be running on your property, end of, no arguments entertained, or if she comes wanting to use your field again - when I'd simply say "no, sorry, I don't want anyone else using it in the future."

You owe the neighbour no explanations nor apologies.

I'm petty enough that I'd report her bonfires though: "It's not illegal to light bonfires, and there are no official restrictions on when how often they can be burned. ... However, there are environmental laws that stipulate against a bonfire causing harm to health, the environment, or to the neighbours' enjoyment of their property by producing excess smoke."

She sounds a properly entitled cow.