She also came home from school yesterday saying 'I was the last one to finish my maths worksheet and I had to be told to stop talking 3 times'. Apparently, the teacher had to help her finish it as she was taking so long....
My DS8 will do this, and I think I finally understand why. He is a voracious talker and extremely social. I have found that he does not view math homework as a solitary activity-- he wants an adult to be right next to him, chatting with him about every problem. If I leave the kitchen table (where he's doing his math work) to work on dinner, he suddenly doesn't remember the order of operations or he'll take 5 minutes to remember 7x7 (7x7 being the simplest part of the complex math problem).
Your daughter may have learned that by stalling she can get the teacher to come "socialize" with her.