As I said, if you can find the actual transcript to the film, read it and find proof that she was underage, I would then be interested in that.
There is no direct proof, of course. And I never said there was. Lots of movies imply but never explicitly state things. My interpretation of the dialogue that is in the film is, given the ton of contextual information about the intention of the writers, perfectly valid. You are welcome to your own interpretation, which is also perfectly valid.
What was said in post production or in a novelization has no bearing as to whats on the film. And please remember they are fictional characters, not real.
I think that what was said in a planning session for a film does have a bearing on what's in the film. The line "I was a child" is ambiguous. The brainstorming session where the writers say "She was 15 but we won't come right out and say it" gives context to that line.
I know that they are fictional characters. But when a film asks me to cheer for a character I find sleazy, that has an impact on my enjoyment of the film.
That's not about me being PC or whatever---it's about how I as a viewer approach film.
On Golden Pond is more powerful because Peter Fonda is acting alongside his daughter, Jane. When I posted about that film, at least one person mentioned how powerful they found it that the real life father and daughter were playing those roles. But their real-life relationship exists outside of what is on screen and the characters they are playing. It is not uncommon for outside context to impact how we feel (good or bad) about a movie and how much we enjoy it.
We just have different takes on the character and given an ambiguous plot point, we have fallen on different sides of how to interpret it.
There's no need to argue about
Raiders of the Lost Ark but I will always bristle when someone tells me that I'm watching and reacting to movies incorrectly.