как ответить на вопрос Does she want to have a dog and a kitten?

Yes, she does want to have a dog

Неверно, если не хочешь выразить усиление. Верно "she wants", а не "she does want".

спасибо за ответ

she does want to hsve a dog

Смотря что хотите сказать - да или нет?Yes, she does. She wants to have a dog and a kitten.No, she doesn't. She doesn't like dogs.