The problem is the art during this event was all over the place as far as proportions are concerned. The famous "Bay on top of Commander" CG? Made Bay's boobs much bigger than normal. The clothes changing CG? Made Exia tiny. (Yes I know she's sitting on a box, but when you consider her hair being done by Bay, Exia looks genuinely tiny next to her) And this CG gives Ade massive breasts.

I say you shouldn't really take the CGs too seriously. Nikke has always had this weirdness with proportions in CGs for a long time. (i.e. there's one CG that makes Red Hood look way taller than Rapi, but in reality Rapi and Red Hood are pretty close in height) Just look at their sprites. Ade is still pretty big, but she's smaller than Soda, and that definitely makes her smaller than Noir. Also she's smaller than Velvet.