It isn’t obvious what Rory hoped to achieve by holding a Donna Reed Night with Dean, or what she thought she had proved by doing so. If she wanted to confront him with the reality of being an ideal 1950s housewife to show him how unrealistic it is, she is only partially successful.
Dean clearly adores the idea of her cooking for him while dressed in high heels and pearls, and even likes the rather terrible food she has prepared from packets and cans. Rory receives reassurance from Dean that he doesn’t really want her to be Donna Reed, but when she says she would do it all again, he is very quick to show interest in the idea. If anything, she may have awoken a desire in him he didn’t know he had.
If Rory planned to seduce Dean with cuteness to resolve their argument, she succeeded – but at what cost? And why? Was she simply scared of losing Dean, and made a grand gesture to win him back? If so, it’s sad, but probably not unrealistic for a teenager, that a single disagreement over an old TV show could make her so frightened and desperate.
There seems to be an element of wanting to demonstrate to Dean that she can have opinions and an identity that differ from Lorelai. Her choice of teenage rebellion is a bit strange, but she seems to have decided that she will set herself apart from from her mother by being far more willing to change herself and her ideas to please her boyfriend. Little wonder the uncompromising Lorelai thinks a blow to the head might have been involved.