mathprofbrony 
"[@Background Pony #904B":](/1133188#comment_4933201
)
In dragon terms, she seems to be closer to his age than Rarity would in pony terms. She is, I agree, noticeably older, but I don't know that she would even qualify as a young adult. Rarity has been owning and growing her own business for years.
It's not easy to tell, of course. In addition, there's the matter of their relative rates of aging, which could make the absolute difference greater but the difference proportional to their lifespan smaller!
In dragon terms, she seems to be closer to his age than Rarity would in pony terms. She is, I agree, noticeably older, but I don't know that she would even qualify as a young adult. Rarity has been owning and growing her own business for years.
It's not easy to tell, of course. In addition, there's the matter of their relative rates of aging, which could make the absolute difference greater but the difference proportional to their lifespan smaller!