I sold my neighbor a puppy for two hundred she gave me one and said next Friday she would pay me the other half. She had to according to her take the dog to the vet because of a hurnia which she says she did not know about and she did. She says she is not going to pay me now. She came to my house to talk about this and started yelling at me and accusing me of threatening her, when my kids were right there I said leave my property and she refused so I called the police. She then left and the cops have yet to talk to her.. I want my money or told her that I would give her the money back and take the dog back. I sold all the other dogs for three hundred.what should I do or what can I do?

You picked the right forum. Small claims.

But I'm not sure $100 is worth the trouble.

Ok, how much do you value the friendship of this person, assuming you were friends.

Are you in the dog business or just had some pups to get rid of.

How much did they spend on the vet ? Did you offer to let them take the dog to the vet prior to purchase ?

So.
1. you sue in small claims court and most likely get your 100 dollars.
2. you tell them you are sorry this happened, and sorry everyone got so mad, you tell them that you will be glad to deduct the vet bill from the 200 dollars, get a copy of the bill and do this, if they want to keep the dog.
3. hey you even offer to just give them back their 100 dollars and tell them to keep the dog if they are attached since you value them as a friend and neighbor more than money.

** if it is only about the money sue

*** if they are a friend and that is important, doing what is outside the box and even taking a personal loss in money is better than losing a friend over 100 dollars.

Another example of no contract - nothing written and apparently nothing understood. I can see Small Claims Court and the argument BUT did the other puppies that sold for more have hernias? If not the sales prices mean little.

I don't know how/why it makes sense to sell a FRIEND a puppy for $300 - the selling price of all the other puppies - when the FRIEND and the OP "knew" that the puppy had a hernia.

Yes, the friend's behavior is over the top but I see a questionable legal argument here.

And I know dogs and puppies.