Pom Klementieff was 29 in Guardians of the Galaxy Vol. 2 when she played the character 'Mantis'.
That was over 7 years ago in 2017.
Today she is 38, and has starred in 33 movies in total, 17 of those since Guardians of the Galaxy Vol. 2 was released.
In Guardians of the Galaxy Vol. 2, I think Pom Klementieff looks: