A bit disturbing?

So when Tom Hanks meets the girl in the police office and takes her home, she doesn't really appear like she is mentally all there. That's the first conclusion any normal person would make when they meet a girl like that, if they didn't know she was a mermaid. Arrested for walking nude, doesn't quite know most of the common things-revolving doors, television etc, clearly giving the impression of being incredibly childish for someone of that age. So it's a bit disturbing that Tom Hanks' character proceeds to have intimate physical relationship right away with such a person. I know it's a movie and I should probably just enjoy. I hate when people do this in message boards. But I wonder if they'll make her character act the way she did if this movie was made today.