You're from the seventies, but I'm a nineties bitch
The girl in the song is in a relationship with an older man. They are clearly leading two very different lives and she felt that their relationship needed to end due to their differences. This difference is best explained through the clear dichotomy between their actual or perceived ages.
Women in the ‘70s were expected to be perfect, mild housewives, whereas in the '90s neo-feminist rhetoric took the main stage. She refuses to be forced into the traditional quiet wife position and will be a loud rebel instead.
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