Narcissistic personality disorder my daughter is 8?

I am very frightened for my daughter.. i dont know what is going on with her. age 1-6, she lived a happy carefree life. she was my baby girl. loved and hugged . we moved, our lives changed, things became harder for us. parents medical problems changed her life. I had a headache, went in the other room to get rid of it, her and her younger brother squabbled. basically, she was trying to order him to do things, she has tried this a lot. tried to be the boss when I am not there. I had already told my son what he could and couldnt do and I told him he could go outside to play because the weather will turn cold and this might be the last day he had. she yelled at him, insisting he had to do his homework first. my head hurt so bad, i could only try to put off the intervention for a few minutes. when i came out, I told her that I told her brother he could play outside and she is not the mother and she does not need to boss him around. truth is, my son is more studious than anything, because, right after he played, he came in did his homework without being told ate dinner took a shower and got ready for bed. he is 7 and he is very resposible and ethical. my daughter is the opposite. after I admonished her for bossing her brother, she says she is going upstairs she walks into the kitchen and "steals" candy. after the big 'talk' last night. Im not ok, shes not OK, she starts humming happily as she is eating dinner. Im horrified. she doesnt have a conscience, the whole "talk" she kept inventing lies for everything, blamed everyone but herself and even got to the point to where she blamed the little person inside of herself who tells her to do things even though she knows its wrong. She doesnt seem to think its wrong, i can tell. I am sorry this is all over the place, but she is 8. i would like to believe that there is hope. of course, Im about to try tough love, but i dont feel like I have the heart, but I have to help her. i triggered her to steal, when I took away her position of authority over her brother, even though she never had it, she just believed it. is there anyone out there who lives with this condition, or children with this condition, and is there anything we can do so their adolescent years arent scarred with pain and misery. The only thing i know is that boundaries need to be tighter. I am very scared for my daughter, It is a cruel world, and I will sacrifice what I have to, for her to be well adjusted, not living in this fantasy