i can understand your frustation. but, please be friendly with your daughter. take her out. main thing is try to find out why she suddenly started behaving like this......i mean did she face any problem outside or in her class or with her friends. try to resolve the issue.
She might be feeling inferior. to bring her out of that situation as parents you need to have loads of patience as the matter is sensible.
Befriend with her. if u r working woman , then you need to find time to spend with your daughter.
Don't stress her in studies. just be cool.
Love and patience is the key.
Win your daughters heart.
I am very friendly with her. Nvr stress her much in studies. Will b ok if she get pass mark. Studies I think secondary to discipline. That€™s my worry. As per my view If a kid is very disciplined it will automatically study. As u said I take her out n get everything before she asks as she is the only child. Inspite she is dominating us. I m going as per her wish in everything n very patience with her. Anyways will wait for a change. Thanks for ur reply dear.