T., my husband and I swear that lice are the worst thing we have had to endure yet as parents. Both of my girls had lice and we struggled on and off for MONTHS to keep them clear. You absolutely have to get rid of every single egg, every school has a "no nit" policy and will not allow them back for 24 hours after seeing an egg on their head. You don't want to keep using the shampoos, they are harmful and not very effective since these bugs started morphing into "super lice".
Getting rid of lice is a pretty big underhaul, you need to wash EVERYTHING in hot water, bag everything that can't be washed and put it in storage somewhere for at least two weeks (stuffed animals, etc). Either steam clean or spray all furniture, car seats, etc. wich lice repellant.. think of ANYWHERE your daughters heads touch.
One of the tricks that we found to work well was to douse the girls head in olive oil and have them sleep in shower caps all night. The oil drowns the lice and suffocates them, it also helps make the eggs easier to slide off the hair.
While the combs seem convenient the only truly effective way is pulling the hair into different sections over and over and pull those eggs out manually. Sometimes the combs pick up eggs close to the scalp only to drop them along the hair shaft as you're pulling the comb away from her head. If it's in your fingers then you can be sure you've removed it.
I wish you all the best of luck! This was a highly stressful and emotional time at my house.