A doujinshi artist on pixiv actually digged up the original model of Tomoko's fashion in Grand Gorgeous 21. It is quite likely that the design was inspired by this magazine issue (July 1993). The headband, the big pearl necklace, the denim shorts, and the oversized layered t-shirts.
I believed the name of the fashion model is 一色紗英 Sae Isshiki. Very cool girl indeed.
So I decided to create an image based on this interesting finding.