In the manga after Mortis tells that Musumi is dead, Saki remembers her mother. For various reasons, few people thought that Saki was also thinking about her mother in the anime, but honestly, the scriptwriters hinted at this. Anyway, later in the anime Saki says that she wants Mutsumi back. And considering what was in the manga, i believe that Saki probably thought about her mother the same way

"I want my mom back". And I felt sad