Woke up to my 8 year old daughter touching me in private places

I have an eight 1/2 year old daughter. She is very agressive in everything she does. She is very disrespectful most all the time she will argue with you over everything because she always has to be right and she always knows everything. Her grades in school are A’s and B’s but her conduct is little to be desired. I am concerned that someone may have done something sexual to her as I was taking a nap the other day she came in while I was asleep and, When I woke up she had her hand down my pants and the other on my breast. I asked her questions for 3 hours but got so many excuses, she first said that her step fahter and I do it that she got it from us. When my husband and I are intimate we always close and lock the door. He works nights and sleeps in the day and I am always at home. She said she got it from a commercial on TV then showed me the commercial and It was nothing like what she described. She said she got it from sponge Bob which I know is not true. She has only been to 3 peoples houses mine, a friend from school and my husbands parents. I am very concerned about her behavior and I don’t know what to do. She is not forthcomming with any information. I want her to be able to open up to me and I don’t think that curiousity would make a child go this far. I spank her I ground her when she needs to be and nothing seems to help she is lazy will not follow directions and will not do what I tell her to. She always tells me no when I tell her to do something. I have honestly had as much as I can take out of her and now this. Where would I begin? We can barely afford to pay our bills now. I can’t afford a psycologist.