What to do

Well my daughter will be 8 in 7 days and I feel like I am losing control of her. She is rude to me and others, I know nothing she knows it all, and she is driving me NUTS... Any advice. I dont like to yell at her I take away her stuff and she doesnt seem to care. I feel like I am failing as a parent and dont know what to do. She has always been very well behaved I never had any problems up till recently but I wanna fix it asap before she gets out of control totally. Uggggh