Hi Madie! I can sympathise - dd has had them twice now, and both times I ended up with them too. They are horrible, sneaky little creatures. They can run fast too, about a foot in 30 seconds, so they can run if they feel searching hands! The chemicals might work on the live lice, but IME you have to physically pull out every nit (egg), or they will hatch, and within a week they lay their own eggs and so the cycle begins again.
The only thing I have found that works, is to cover the DRY hair with conditioner, heaps of it, which stops them being able to run away! Then use a fine metal comb, and go through it over and over, rinsing it off in a strong vinegar-water solution. The vinegar dissolves the "glue" they use to keep the nits on the hair strand. It does work, but you have to be ruthless and tough and do it EVERY DAY for 10 days to break the cycle. If you miss just one baby louse or one egg, you will have to start all over again...so be thorough no matter how much it drives you crazy!
HTH and chin up, you will win!!!