Is it permissible to deal with a sister who causes marital problems by requiring prior notification before a visit, and by not opening the door if no notification is given, and by treating her like any other visitor without allowing her to roam freely in the house, and would this be considered cutting off ties of kinship?

It is permissible to obligate the sister to give prior notice of her visit to conceal what the questioner does not wish her sister to see. It is also permissible not to open the door for her if she has not sought permission beforehand. Preventing the sister from wandering around the house and looking into private matters is not considered a severing of kinship ties. Kinship ties are maintained through visiting, greeting, and exchanging gifts, not by prying into people's private affairs. All of this should be done with wisdom, gentleness, and consideration for the sister's feelings to avoid estrangement and mutual animosity.