"Fruit Version: My Big Sister and Me" is a rather early anime that was released on 1985/12/8.
The story features the sisters Maki and Nami, with Maki being the younger sister.

https://archive.org/details/travelingfantasiesdvd

If you like, you can throw in "1980s (style), retro artstyle, parody"

School Uniform:

fv_maki, 1girl, aqua eyes, blue eyes, black pupils, (eyelashes:0.6), green hair, medium hair, curly hair, bangs, hairband, yellow hairband, school uniform, jacket, blue jacket, collared shirt, white shirt, long sleeves, neck ribbon, red ribbon, blue skirt, pleated skirt

Casual Outfit:

fv_maki, 1girl, aqua eyes, blue eyes, black pupils, (eyelashes:0.6), green hair, medium hair, curly hair, bangs, hairband, yellow hairband, sweater, pink sweater, collared shirt, white shirt, long sleeves, red bow, red bowtie, blue skirt, pleated skirt, miniskirt