Don't use a lice comb. You don't need one.
Wash her hair with regular shampoo and then a good conditioner. Comb out all the tangles while the conditioner is on her head in the shower.
Leave her hair dripping wet and section it off into several sections then clip them up. Take one section and use a regular comb, like a rat tail comb, a small black comb that men use, a regular comb and take about a 1 inch section and pin the rest back up to keep it wet.
Go through that one section of hair. Start at the bottom and comb through it. Use a magnifying glass head gear so your hands will be free. Then if you see a bug it will be sitting still. The water very nearly drowns them and they are weak. They can barely move and since the hair is wet they are in a hostile environment. They are easy to see and pick out. Drop them into a glass of water.
Keep her hair drippy wet to keep the critters stunned/slowed down. A spray bottle can help with that.
If you see a white egg it's empty and will likely just slide down the hair shaft. If you see a nit with a black center, that's a baby inside. That one needs to go into the glass of water too. It might be harder to slide down the hair but if you use your nails and pull gently is should come off. IF it won't you have the option of snipping that single hair out but don't do that unless you just have to because if there are a lot of them you'll end up with a child with hair that's almost in a buzz cut...
After that one section is done you pin it back up and go to the next. Keep the hair drippy wet and it will go easier.
This is the healthy non-treatment way to get rid of lice. Those combs are cruel inventions and a way to make you spend useless money.