Don't use /skip in this case, use /branch.
/ branch = [if (radiobuttons.gender.response=="female") surveypage.femalefollowup]
/ questions = [1=gender; 2=age]
/ questions = [1=stuff]
/ questions = [1=stuffpuff]
/ caption = "You are"
/ options = ("female","male")
/ caption = "Your age"
/ caption = "Because you're a woman, write stuff here:"
/ caption = "and now press the back button to get back to the demographics page…unfortunately it will lead you to the femalefollowup page as a male and female"
/ pages = [1=demographics; 2=funnybunny]