Valentina Kerman is the first known official female kerbal which doesn't use the same look as the other kerbals seen in version 0.90.0 and before. It is not known if there will be an actual Valentina Kerman predefined like the other the original three or if she is just the prototype of random female kerbals.
In real life, the first woman in space was Valentina Tereskova (Russian: Валенти́на Терешко́ва). Valentina Kerman, as the first female Kerbal, is almost certainly a nod to her.
At age 26, Tereskova flew aboard Vostok 6 from the USSR on 16 June 1963, logging a then-record 48 orbits within three days. For 19 years, she also remained the only woman to have flown in space.
In 2013, at age 76, she said she was willing to take a one-way trip to Mars.