Is it permissible for a woman to wish to marry in Paradise a man she loves who is already married? And will a divorced woman marry her ex-husband who died without taking her back? And what is the meaning of "taking care of her" (القيام بها) in the context of the benefits of marriage?

It is not impossible for a woman in Paradise to marry her divorced husband or another man, if she desires it and she died not being in the wedlock of anyone. A woman must turn her heart away from attachment to a specific man if marrying him is not feasible, and she should occupy her time with what benefits her in her religion and worldly life. Matters of the Hereafter are not to be measured by matters of this world.

The summary of Shaykh Ibn 'Uthaymeen's words, may Allah have mercy on him, is that if a woman in Paradise desires to have a husband, she will marry. He based this on the generality of Allah's saying: "And for you therein is whatever your souls desire, and for you therein is whatever you request" and His saying: "And therein is whatever the souls desire and [what] delights the eyes, and you will abide therein eternally." So, if a woman is among the people of Paradise and has not married, or if her husband is not among the people of Paradise, then if she desires to marry, she will certainly have what she desires. And the statement of the author of Ar-Rawd (al-qiyām bihā) means undertaking the affairs of his wife, such as providing for her, protecting her, and covering her.