Give him to a shelter, a rescue organization, a farm, another home, but do NOT kill him.
I'm sorry, but this is an incredibly naive and dangerous thing to say. The absolutely worse thing a person with an aggressive dog can do is to dump the problem on someone else.

An aggressive dog will be the first to be euthanized at a shelter. Even Best Friends will not take dog-aggressive dogs. Shelters have a limited amount of space, time and funding. They must take the most adoptable dogs, and the rest are euthanized. If the dog needs to be euthanized, it should be done by its owners, in a loving, safe environment - not done at a frightening, loud shelter by strangers. People dumping their problem dogs at shelters is one of the reasons the euthansia rate is so high. It's wrong, and it's an incredible cop-out, and I'm so very glad to see Ash is mature and responsible enough not to be considering this very bad option.

It is my understanding that Chewy is not a purebred dog, and therefore a rescue organization if probably not going to take him. Most rescues (not all, but most) specialize in purebred dogs.

Giving an aggressive dog to a farm or another home is simply ridiculous. Chewy already has a good home, with lots of love and attention. The home is not the problem, the dog is. What difference does it make if it's a farm or not? A farmer is not going to want to be bitten by a dog any more than someone in a city is. And the first time the dog goes after livestock it's going to get a bullet in the head, I promise you.

My personal opinion is that Ash is fully aware of all the options that she has. Everyone has given her good advice and listed a lot of choices. However, we all need to keep in mind that Chewy is her dog, and she is the one who knows him best, loves him, and has to live with him and deal with his behavior and the consequences of that behavior. It is not up to us to judge or criticize her for the choice that she makes. We are not the ones walking miles in her shoes.