I think that person might be the flower near Asgore's cash register.
Dialogue proves that this person is a flower
AND they run a shop specifically, because they are near the register.
They are important enough to have a human form like other flower, but not important enough to have a shown face or a proper name. And the flower at the register in the Light World looks just like the other 7 on the second floor, but is not at all important to us.
The only downside to this theory, is that there's dialogue that implies this flower might possibly be white ( or extremely light coloured ), since it's name dependes on the colour it reflects.
BUT I STILL THINK I'M ONTO SOMETHING
























