How to get rid of LICE?

my friend in india has got lice for almost a year now. she has tried mediker shampoos and oils, manual picking out the adult lice using plastic combs,she's even used cockroach sprays hoping that if the sprays kill cockroaches then why not LICE?, she also grinded the neem leaves and made into a paste and applied it onto her hair keeping it for 1 hour and then shampooing it removing lice with the lice comb, also the maynnaise thing. however the lice and the eggs have not gone completely. pls help by giving easy home based methods without any side effects.