first i would like to say good for you guys being such a loving close family! i wish EVERY family could be like yours!
It does sound like tween drama!
you need to find something that really speaks to her as a person to help her understand her behavior.
as her mother you probably know her best.
what is the thing that she needs the most right now?
she sounds like she likes attention! like my kids!
if so, she will do anything and everything to get it, bad or good.
what you can do is make a chart for her (make it look grown up or "cool" with her favorite colors, pictures of her favorite things to do or her friends and family)
put all the things on the chart that you need her to do, or want her to do, like chores (be specific, clean room, scrub toilet, etc) general cleanliness like brush teeth, shower, wash hands, etc. used kind words when upset, calmed down when angry with sibling or parents, apologized for being mean or saying a bad name etc.
then when she does each good thing on a daily basis put an awesome glittery sticker or check mark wtih a pretty sparkle pen, if she did NOT do them then you can take a big red or black marker and make an X.
at the end of each week she can earn a reward for all or most of her stickers, such as a special outing with mom, like dinner and movie or frozen yogurt or ice cream, or walk to the park, or skating rink or theme park or whatever fun thing she wants to do, you can let her pick!
my kids get coupons for special outings with mom or dad. they LOVE it
the key is to BE CONSISTENT, it really works, especially after the first time.
and if she earns a reward then does something bad you take it away (its not a physical thing, but its positive attention specially for her)
if youre like me you can also let her earn it back by doing something extra special like writing a sorry letter to a sibling or doing extra chores or making dinner for the family! (with adult supervision)
it teaches compassion and responsibility.
bless your family and
Good LUCK!!