From what I understand, the power uses life stan, so like the emperor, she has twice the normal life span. So, I'm assuming she will grow twice as slowly until her core is unlocked, and then from that point, after using the power and burning the excess life span, she will start to grow normally.
Continuing that chain, I guess if she overuses her power, she would be expediting her age and could, presumably, at some point, look much older than her body's actual physical age.
Which, well, is another ethical conundrum, I suppose.
Cause I still haven't figured out if she defines herself by her past life, or thinks of herself as a seven year old but with the memory and maturity of an adult.
If it's the former, then her body will fit her age, but if it's the latter, then it will be like you were saying but opposite. A ten year old with the body of a twenty year old... and no lol. Yikes. Yikes. Yikes.
Wait so since she’s a primera and ages half as fast as normal people, does that mean she’ll look ten when she’s 20? Cause if she was getting married then that would be creepy for the person marrying her.