I am playing the game on Vsmart 4 and Joyplay. The quest is the lost elf, you can see for yourself in the video.
So as I try the other option, Mantida is normal with no star on her head.
If I'm not mistaken, you may also have seen two almost identical texts in a row in the end of Sarnara's event. If so, I've fixed that bug and it won't be in the next update. Thank you, with the video it was incredibly helpful. It's actually the very ending of the quest, so I don't think this star will make you any troubles.
Also, I'm just wondering how the game goes on the joyplay. Doesn't it crash or something? I remember I was asked about joyplay, but I could not answer as I have not tested the game on mobile devices.