The first question....do you have rights? Absolutely. The second question though...is your husband inviting her over? If so, she would be violating the law. If either you or your husband invites someone over, that person is granted permission to be there and as such they aren't violating a law. Does your husband want her there?
You have rights in the house. His sister may come if he invites her.
To the PROSPECTIVE client, please call myself or another attorney for your choice with more detaiils and an appointment. My PRELIMINARY answer to your question(s) is for general purposes and based upon what little information you have conveyed. It is based on such limited information that the general answer should never be relied as a reason for your action or inaction. My response does NOT establish an attorney-client relationship and such may only be established by mutual agreement, and the signing of a written retainer agreement, which will generally require payment for our services, as this is what we do for a living and, just like you, we must get paid for our work.. .