It could be argued that even among humans, some definitely require 10 or more years to reach the same maturity level that others have in a much shorter amount of time. Couple this with an alien origin and it works for me that she may have a different timespan of adolescence. Even though her DNA was patterned off of a human, it is clear that it isn't 100% or she wouldn't have had to battle her Plodex urges...