Buying a puppy: can a seller simply cancel the purchase?

Questioner

My sister wanted to buy a dog. She first visited a recognized breeder and he had referred her to a couple of friends who were having a litter. She contacted them and the seller wanted to sell her a puppy. When the puppies were born, my sister received a message via the watts app that she was getting a puppy. She sent photos and videos of the puppy every week. My sister visited again, and the seller would keep 1 of the 5 puppies herself. She got to see the puppies at the window, because of corona. Last weekend the seller sent photos again. Last Monday her husband called my sister and said that she was not getting a puppy. They had a gut feeling. At the time, the price was also discussed on the app and that a written contract had to be signed. My sister and kids are completely devastated. They had already purchased things and had also kept informing this lady of the preparations they had made. After this phone call, my sister contacted her. The lady did not answer, only when she called from an anonymous number did she answer. She did not explain what had suddenly changed and she blew the horn on it. The question is whether this is an agreement that the seller must also comply with.

Lawyer

Yes, the seller must deliver the puppy unless she cannot do so for a valid reason. (for example, death of the puppy.) In that case, the seller will have to be put on the waiting list again or the purchase will be cancelled and the money will be refunded. The reason you mention is not a legally valid reason for termination.