Here are the two main line up, that were created during development stage. These are the correct relation-sizes.
For everyone who wanted to know who is taller: Talia, Auriana, Iris, Lyna or Carissa.
Fun fact : on their magical outfits, both Talia and Auriana are taller since they now have high-heel. But Iris already had heels on her casual outfits, and creators didn’t want the relative size of Iris-Talia-Auriana to change when they are in magical mode. So they cheated : they made Iris a little taller in magical outfit to preserve the relation size we liked in casual form. “It’s magic”.
Another model sheet with Lyna, Carissa, Izira and Lev. Basically, Lyna is a little smaller than Talia but taller than Iris, and Carissa is the same size as Iris. The “trick” with Iris’ height is applied also with Lyna and Carissa, so the relative relation size between them stays the same, being casual outfit or magical outfits.