She cleans and cuts all her nails, both finger and toe, as well as making sure there is no food between her teeth. She must clean her ears, and every body cavity. She must remove all makeup. She must comb out all her hair completely. This means all hair she has everywhere on her body.
Many women take the bath at home, and do the follow-up shower at the mikvah.
When going to the mikvah, she may not have anything between her and the water at any part of her body. Therefore she must remove all jewelry, makeup, etc. This is why she should not get a haircut too close to going to the mikvah, because sometimes small hairs are hard to get rid of after a haircut. There is supposed to be a woman attendant at the mikvah to help you check that you are ready for the mikvah. You may have to call the mikvah in advance to make sure she is there that night.