So, I just had a sudden insight.
[X] Continue to be empathetic and calm. Getting mad at Oriko won't help anything. Continue being affectionate toward Mami to keep yourself calm.
[X] Offer Oriko hope and support as she deserves them.
[X] Agree that it's difficult to change yourself just by thinking it.
[X] Reassure Oriko that you know it's possible, if difficult, for powers lost from rejecting a wish to come back.
[X] Furthermore, point out that she doesn't need her powers to be able to help or find the meaning of her life. After all, Kirika wished that she could help Oriko, and the power her wish gave her was anti-magic.
[X] Bring back up the topic of finding the meaning of her life. Suggest that rather than trying to make others happy, she tries to find what makes her happy.
[X] Ask Oriko and Kirika if there's anything you can get them to help them pass the time (books, games, movies?), then depart and ask Homura for a timestop.