hi can anyone advise me on what to do about my 13yr old girl, she is always mouthing off at teachers and getting in trouble for it, also for things she tells me she has not done, i dont know weather or not to book her in at the doctors to see if she has behaviour problems she is getting worse.

I would say don't go to the doctors yet, It may be the age as she is growing up and testing the boundaries with adults.
Ask round see if her friends are mouthy, she maybe getting from them.
I have friends with teenagers who are mouthy and getting into trouble and My little girl is 8 and gets mouthy at times as she goes to Junior school now and isn't a little girl anymore. At times i feel I have an 18 yr old!!
So your not alone it will get better