Though she was born years after the decade ended, Olivia Rodrigo has mastered ‘90s style. Whether she’s wearing Vivienne Westwood-inspired tartan corsets, Blumarine ra-ra skirts, or vintage cheerleading outfits with black creepers, the 18-year-old music star has spent her stratospheric rise to music stardom over the past year showcasing her irresistibly fun, pick-and-mix approach to turn-of-the-millennium fashion in all its glory. Attending the opening of the…