Behavioral is usually purposeful to the doer (even if it is unhealthy or dysfunctional).
She would need some sort of a routine where she knows 1/ what is expected of her and 2/what the consequences would be if expectations are unmet.
It may be helpful to sit down with her and both of you come up with some guidelines. These you may want to have her write and post on the fridge or someplace like her mirror in her room where she would be reminded of it. As she is getting older, you can't be the one ensuring that she follows these rules.
She would need to start relying on her self for that. If you have been the one responsible for it in the past, it may have enabled her to rely on others for queues to know what is acceptable and unacceptable behavior. Hence, she may have started to overly rely on others, and if there is no consistency in consequences some of the time, it can either 1/confuse her about what her exact role in this is and 2/what to expect as a consequence.
When the two of you sit down to come up with a list of what are some of the usual issues and her past reaction in each scenario, ask her to identify 1/ her role in it (what she did at that time, was she thinking ahead of what would happen or was she impulsive 2/ how does she think it is making the other person feel and 3/ what are some of the queues for her to know if she is engaging in this pattern again 4/ what can she do before things go on too far. She can write all of these for her own self reference and to actually put down on paper and see how much of her behavior may be contributing to what takes place.
Even though you all may be busy at home, try to have a family meeting once a week (pick the same day and time) where you, her brother and she sit down and go over concerns that each of you is dealing with and coming up together as a team with solutions to these.
Think of entrusting her with specific tasks that would allow her to feel a sense of belonging to the family unit and to feel pride when these are accomplished.
Adlerian psychology believes that a child acts because of 4 things:
"Undue Attention - All children desire and need attention. But a child who needs attention all the time will resort to behavior to keep others busy with him or get special treatment. Parents will feel annoyed, irritated, worried and/or guilty. The parent responds by scolding or warnings and the child is temporarily satisfied but not for long.
Power - For some children their mistaken goal is to be in charge and be the "boss". By their misbehavior they are saying "I am in control" or "You can't make me". Parents feel provoked, challenged, angry, threatened and/or defeated and will meet the child in a power struggle. If the parent gives in the child "wins" and stops the behavior until the next power struggle arises.
Revenge - These children often feel they have been hurt or that they can never win in a power struggle. They feel the only way to belong is to get even. Parents feel hurt, disappointed, disbelieving, disgusted and rejected by this form of misbehavior.
Assumed Inadequacy - Often a child will just give up displaying helplessness. They want to be left alone so they have no expectations to live up to. Parents feel like giving up, doing for, over helping and helpless to do anything. For many children this form of misbehavior is displayed only in certain areas like homework or activities.
These four goals of misbehavior give parents the clues they need to redirect their children and help them find positive ways to achieve their need to belong. Understanding that children are not consciously plotting their misbehavior but it is based on a child's mistaken goal, goes a long way in promoting a respectful parenting style"
These are based on the STEP (systematic training for effective parenting) module.