ANSWER:
It is every woman’s right in Islam to have a separate accommodation after marriage.
Yes, you have the right to reject a proposal if he is not ready to provide you a separate accommodation. However you must not keep rejecting proposals like this as it would become very difficult to get good ones after you cross a certain age. You should settle even if he is ready to give you a separate accommodation in the same house as his parents, with a private room, a kitchen and a washroom for yourself.