User blog comment:Koishi-Komeiji/Rumor of the Ten-Thousand-Year Sakura/@comment-4802891-20191201172825/@comment-24965192-20191201174021

Yes, if her Rumor self is summoned, she is an Alter Ego.

Besides her and Holy Mami, there's also Holy Alina and Rumor Tsuruno. Holy Alina's insanity (heightened due to the Rumor) essentially takes over the Rumor's control, so she is not an Alter Ego but a Berserker. Rumor Tsuruno is Tsuruno Yui combined with the Rumor of the Chelate Mascot, and she is an Alter Ego.