What should we do with these alcoholic beverages, and will God hold us accountable for what my sister has done, given that she lives in our house?

Enjoining good and forbidding evil, and loving good for Muslims, are obligatory. You must advise your sister with wisdom, gentleness, and patience, and not despair of her reform. It is obligatory to denounce and remove evil, such as pouring out intoxicants and disposing of them and their containers, while continuing to advise and admonish, accompanied by threats and reprimand when necessary. If the sister does not desist, she should not be allowed to reside in the house; in order to prevent the entry of evils. There is no sin upon you for what she did if you remove the evil from your home. You must continue to advise her and call her to Allah, hoping that Allah will guide her.