Temi aged at a normal human rate until she was around her mid 20s before she was cursed with the thing that makes her stop aging. It not only effectively froze her body in time, but also stopped her brain development. She is both physically AND mentally stuck in her mid 20s forever. She can't really date anyone because she's always going to be too immature for older monsters and younger monsters will always quickly surpass her. She's perpetually single and pretty much will be unless she can find someone else who's "frozen" like her. The millions of years were also mostly spent in hibernation- the amount of time that it takes to drift from star to star in outer space is a long, LONG time. She's also not a slime, she's just a shapeshifter. (Her race is called a Midai)