Sleep problems and co-sleeping!

Hello people!

By the title of this post you may be forgiven for thinking this is a post about a toddler not sleeping.  Although I know this can be a huge problem for people this post is not one of those. 
Our daughter has recently started having sleep problems.  Now our daughter is eleven years old, shes not a baby and sleep problems are not a situation we have experienced before with her.
She is unable to sleep unless she is in our bed. 
Now  I am a huge advocate of co sleeping.  I co slept with our three boys and this was a huge success for us.  Each of then eventually slept in their own beds at around the five year old age.  We didn't co-sleep with her as she didn't like it from being a baby.  She much preferred to be in her own bed/cot.  So why now?
As much as I advocate co-sleeping, trying to sleep with two (not small!) adults and a eleven year old, plus the dog (who sneaks in when we are not looking), all in a king size bed is not conducive to a good nights sleep!

We've gone through the normal things with her. Stress, trouble at school, worries etc etc.  We've even checked that her room isn't too hot or cold.  She has a huge king sized bed with plenty of cushions, teddies, pillows and the like.  She has slept in the same room for five years so its not that.
We are at a total loss. 
Any ideas lovely readers?  Answers below please!!!!!!