Perhaps i'm overstepping here but me and the main man
@recreation had bit of a discussion about Ellie and the potential underage angle during the time i was checking his first draft for him, with his permission i'd go into detail, it's quite interesting from a game design perspective IMO.
Though he didn't state it outright Ellie was intentionally a bit of a late bloomer all along, sort of adds to the mute and emotionally troubled thing, it just seemed like a natural extension of her other areas of slow development to me that she was quite young for her age, that and obviously he wanted to hit the cute meter up to 11, i think he managed both personally while keeping himself out of hot water with patreon and loli.
@Demoness_Kiss you may be right about the faking it, i could be wrong but i don't think she is, i think she saw something that night she went walking, something really significant, something dark, something most likely sexual, i don't know for sure and even if i did i wouldn't drop spoilers but think about the cast you've seen so far, who is old enough at the time of the PC leaving home to be doing dark and terrible things, well the suspect list is small, Mom, nah, not a chance, Dad?, maybe, he is a bastard and a half and no mistake, or the dark horse of the list IMO, the police officer, dun dun dun!!!