100+ years old but looks like a kid

what are y'all opinions about like the mc's lover looks like a child but is 100+ years old because she/he was a dragon, or demon idk

Because for me it felt weird why? Like imagine showing your girlfriend/boyfriend to the people around you who literally look like a child who didn't even finished elementary, and if like yk dogs years like when they're 5-6 months they're teenagers or something, and so does dragons, ik ik they're human what do u except? But then doesn't still that mean they're still a child? Because they evolve like to child and until to adult