Well it's a good thing these stories are fake. The first time I heard it was from a standup comic where his grandma gave him a bible when he went off to college and she said to read it any time he needed money. In the pages was a note telling him to fuck off.
Gifting someone something and taking the time to write a thoughtful note is a very nice thing people do for each other.
Typically you respond in kind with a “thank you for the gift and the card/note/well wishes attached”.
These are what would be considered “polite social norms”.
The girl slipping a note in to the gift and saying her feelings also is not crazy. It can be hard to put yourself out there.
HOWEVER if someone straight snubs your gift it’s gonna be shitty even if it’s from a friend. He snubbed her, she got the message even if he didn’t know he was answering.