What should I do about my underage stepdaughter who repeatedly commits zina (fornication/adultery), knowing that expelling her is not possible, and is it permissible for me to seek a divorce due to my discomfort with her presence?

It is the wife's right that her husband provides her with an independent dwelling with its own facilities, and he is not allowed to compel her to live with any of his family members except with her consent. If the husband stipulated before marriage that she live with his daughter, then she has no right to demand a separate dwelling. If the daughter is residing in a house with shared facilities and this was not stipulated, then the wife has the right to object. However, if the wife has an independent part of the house, she has no right to object. Living together does not become impermissible due to the daughter committing sins, as long as the wife does not assist her or condone her actions. It is advisable to be patient and cooperate in her upbringing and reform.