If your daughter is listed as living in your home, your health insurance plan includes her up until the age of 26. If you attend college in another state, your health insurance will still provide coverage until she is 26, as long as she is either enrolled as a full-time student or uses your home as her primary address.
If your daughter lives in a home other than yours, she is probably considered an emancipated adult, which means that she is responsible for all of her own bills and insurance policies, including her health insurance. Because she maintains a separate address, she cannot remain on your health insurance, as much because health risks differ by zip code as because she is not considered a dependent if she has her own home.
If your daughter has recently moved out of your home and into her own, she may be able to use your insurance for a while longer under the COBRA act. Under that piece of legislation, the insurance company must extend coverage to her for up to 6 months if your daughter agrees to pay the full amount of her health insurance premiums, which is considerably higher than the premiums offered through your group health coverage.
If these options cannot be applied to your daughter, she will have to find her own health insurance coverage. She may able to qualify for discounts through your insurance company, but it will have to be a policy of her own. Once she joins the adult community, there's no going back to life before she was emancipated.
Your daughter might be well-advised to research her health insurance options online, using a website that provides free insurance quotes. Once she has filled in the necessary information, the site will provide her with an estimated premium and will even compare the cost of buying that policy against going through another company.