Is the mere growth of a small amount of fine hair around the vulva sufficient to make a girl accountable under Sharia, or is it necessary for there to be abundant and coarse hair for puberty to be achieved and for her to become accountable?

The signs of reaching the age of legal responsibility (تكليف) are: completing fifteen years of age, or the growth of pubic hair, or the emission of semen with desire. For a woman, menstruation is an additional sign. The hair that indicates puberty is the coarse hair around the pubic area that needs shaving, not fine hair or beard and mustache hair.