my little sister was just the same, i on the other hand was a bit of a goody goody and did it as soon as it was set!
At 11 i wouldn't worry too much, i know as a parent you do. Perhaps the punishment she would receive off the school for either not doing it, or not seemed to have put a lot of effort in to it may give her the kick up the bum she needs!
I know my little sister didn't listen to my mums persistance at all, but as she got older and began to care more about her work and the realisation of what good grades meant, she put the effort in.
Failing that, possibly ban TV or cut pocket money etc until you see her homework is done. Or perhaps try and become more involved and interested (not that im saying you are not interested at present) and do bits of the homework together, not for her by any means, but just make the process more enjoyable than a chore!
Good luck, i have another few years before i face the trials and tribulations of getting my daughter to do homework!!