Yes this is during the last scene where Yuuta is about to propose to Rikka and Shichimiya appears the text says that "That 's too bad Rikka-chan", "I might still have a chance", "Magical girl Satone Shichimiya"
Essentially yes, Rikka had lost her powers as the Tyrants eye since the start of volume 4 and everyone from the club were trying to help and get it back. Towards the end Yuuta realised that he was the cause for Rikka losing her powers and was going to tell her that he liked her with her powers. Shichimiya wanted to intervene before this as if Yuuta was unsuccessful in bringing Rikka's powers back she would still have a chance. This however was now how it ended and Rikka regained her chuunibiyou
Is this from the novel?
Yes this is during the last scene where Yuuta is about to propose to Rikka and Shichimiya appears the text says that "That 's too bad Rikka-chan", "I might still have a chance", "Magical girl Satone Shichimiya"
Is she still trying to steal Yuuta away from Rikka here?
Essentially yes, Rikka had lost her powers as the Tyrants eye since the start of volume 4 and everyone from the club were trying to help and get it back. Towards the end Yuuta realised that he was the cause for Rikka losing her powers and was going to tell her that he liked her with her powers. Shichimiya wanted to intervene before this as if Yuuta was unsuccessful in bringing Rikka's powers back she would still have a chance. This however was now how it ended and Rikka regained her chuunibiyou
Ah, I see. Thanks.
Shichimiya, start with this attack FIRST next time!