My 5 year old daughter is #2 out of 4 she is the oldest of 3 girls. Recently she has started doing things really out of character for her. She is usually a very sweet, respectful, obedient child. However she has started fighting a lot more with her older brother, she has cut her own hair, colored on my walls, and just today poured a bottle of water down the heating vent. I am very confused, I don't believe she is crying out for attention, she gets plenty as well as one on one time with mommy and daddy. Feeling Lost.
Did you try and ask her why she does it ? If you ask her each time she done something without too much trying to making it feel like an interrogation, maybe you'll get somewhat of a similar answer between the acts.
Make sure you let her know that what she did was wrong, but that you are also trying to help her and be on her side. If you are 100% sure she is not trying to get more attention, maybe that's her own way of calling for help.
Also, try to know if there has been any noticeable change (at school, at home, with her friends, etc.) in her life that she might be responding to.
We had a similar issue at a similar age with our normally well behaved son, the second of three children and the first of two boys.
The issue appeared to be that our son was getting old enough to want to do more things independently, rather than just following the lead of his older sister. Doing things independently meant that he had to handle more conflicts with his younger brother trying to get in on whatever he was doing; previously he could depend on his older sister to handle his younger brother, but that was no longer the case when he was playing independently of his older sister. This desire for independence might have been increased due to influence from full time kindergarten at school.
Our solution mostly amounted to recognizing his increased maturity and independence. We treated him more as an older sibling of the younger child rather than just as the one of the younger siblings of the older child. He got some responsibility for and authority for defending himself against the younger child as long as he exercised the restraint appropriate to an older sibling. We also gave him some 'older sibling' responsibilities, such as being an authorized person for his younger sibling to hold hands with in parking lots. With respect to his older sibling, we made it clear to her that his participation in her play sessions was voluntary: he was allowed to turn down opportunities to play with her when he wanted to, as he was no longer just the minion she had previously treated him as.
We also gave him more one on one time than he had been getting, though from your question you already seem to be doing that.
Now, a year later, this approach seems to have worked pretty well. There are still conflicts, but he's back to being the well behaved child.