well she should be able to get it thru her school... and if shes over 18 her parents shouldnt be able to find out....
if she doesnt like that or cant afford it thru the school look up the closest planned parenthood (
http://www.plannedparenthood.org/) and she can go there... and they can provide them free or nearly free... there are some exams to make sure she is in good health and whatnot... but nothing that shouldnt be done regularly anyways...