How many girls have been to space?

About 10 so far.

======================

Answer #2: (Update)

55 different women total including cosmonauts, astronauts, payload specialists,

and foreign nationals have flown in space.

-- 6 different female cosmonauts have flown on the Soviet/Russian program

-- 1 female astronaut or taikonaut has flown in the Chinese program

-- 48 different women have flown with NASA. 43 of these were Americans.