First let me start by saying that this is a phase that all of our kids about this age are going through. I think it is partly kindergarten, and them being around many other kids, struggeling to get their way and feel like they are getting attention, even if it is negative. All I can say is it is time for YOU to TAKE CONTROL NOW. You will be the bad guy for awhile, but who cares if it is turning you child back from a brat to a child again. So first, praise good behavior. EVERYTIME she back talks you, you make sure you snap and tell her you will NOT tolerate disrespect and that you are the parent, and she is the child. I am going through the tail end of that with my 5 year old daughter, and I have come to the conclusion that I had spoiled her and let her get away with toom uch in the past. She tested me, and I have always "chose my battles"- so to speak...but in the process of trying to do what I thought was right, she got a little bit too confident. So now, I, like you, am turning the tables and discussing mutual respect in relation to each of our roles, mother and daughter. We talk about appropriate verus inappropriate behavior. Ways to voice how she feels, without continuing on her nasty new habbit, that will no longer get her anywhere, but in trouble. Situations and attitude. My daughter is an only child and I am a single mother. We are together, just she and I, all of the time when she is not in all-day kindergarten. I never meant to spoil her, and I look back and it is obvious. It is so much fun to let the kids have their way, if it doesn't mean too much to me- right? So, again, when my daughter starts that behavior- I stop her in her tracks...and firmly...let me repeat FIRMLY and SWIFTLY let her know, it will not be tolerated AT ALL. How you punish when necessary is up to you..however severe. But be very serious, make sure your husband verbally supports you when with the child, and always always always follow through....even if it means changing the privillaged weekend fun plans. With the others that may be around and your husband may not be, make sure there is NEVER any laughing because it, as you know, IS NOT CUTE. It would only create your monster to grow! So have others give a look of disapproval and ignore the child until the child is looking for positive attention and deserving it. Be sure to talk about what others think of a well behaved child versus a backtalking little brat. All in all, I think your child will want to change their attitude. No one likes to be thought badly of. And no child likes to know that others don't want them around when they act that way. Keep repeating those things and keep up the praise. REMEMBER- ACTIONS SPEAK LOUDER THAN WORDS...SO ALWAYS REACT AND ALWAYS FOLLOW THROUGH.
Good luck D. and to your daughter as well.