I don't think I've ever seen them standing next to each other in official art before, but Frenda being as tall as Mugino feels very wrong to me. I know this version of Mugino is slightly younger than her Railgun S appearance, but that shouldn't be affecting her height too much, so I guess Frenda being a perceived as a loli for all these years is just blatantly wrong, since I've never seen Mugino referred to as an oppai-loli.