All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Your husband is a man who has an independent personality and a brain by which he thinks and assesses things and chooses between them when they are conflicting. So, he does not need any guardianship over him from anyone.
He absolutely does not have to listen to what his wife says nor does he have to listen to what his sister says. Rather, he may only listen to what corresponds to the truth and what leads to achieving a benefit.
Of course, he may seek the advice of whomever he wishes among those whom he thinks that they may advise him to do what is good be it his wife or his sister or anyone else. There is no doubt the first person he may seek advice from in regard to matters relating to his marital life is his wife.
Dear sister, you should know that many a time the sister of the husband is jealous of his wife, so it is not strange that the sister of your husband says such statements out of jealousy to provoke your feelings. Therefore, you should avoid her and refrain from responding to her as much as possible. It is even better not to respond to her except in case of necessity.
Moreover, it should be mentioned that as a wife, you have the right to a separate accommodation as clarified by the jurists . For more benefit in this regard, please refer to Fatwa 84068.
Therefore, you are not obliged to live with the sister of your husband in her house or in any other house where you do not have separate amenities.
Allaah Knows best.