If this was chapter 1 my answer would not be her, but unironically the most normal girl right now is Yumi.
Yes, she is a poor girl with abandonment issues AND a Yakuza princess, but apart from that, she posseses the most common sense out of anyone. How many times does something absurd happen only for her to be the only one to see it for what it is and call it out? Her origins might be extremely rare but her behaviour is something you could actually expect from a normal person. From being mean, rude and straight up heartless due to her upbringing to maturing emotionally, now she's just a normal girl who's got a bit of a character and is going through hard times, but that's it.
If I had to choose second place... ofc it's Noriko (again) She is a disgusting brony that wants to fuck her teacher and all of her friends, and her sister is a super famous idol that everybody knows, but that's kinda it?
Everybody else is literally worse in olympic tier of metrics.
Before anybody says "Otoha" again, she's literally a predator worse than Akira that would immediately try to rape a cute little boy as soon as she saw him. Touka and Ayane behave the most normal, but they are secretly psychopaths capable of murdering in cold blood, and everybody else is broken beyond repair, sexually deranged, mentally insane, or all three of them together.
The better question to ask here is "who is the second most fucked up girl" because there's probably no argument against Ami being number 1.