What on earth is that going to help??? Nothing at all, that is absurd.
I do agree. I've never heard of it. Are you sure she knows what bending is? How long has it been since you've asked her to bend? I'm not being snotty, just curious. I agree, .Delete.. Try getting her to bend before you start lunging her. She is a small girl, do you ride her at all? If you do, try collecting her then asking her to cantar. Work with it maybe off her back, untill she gets the general idea of cantering while bending. Then try it on the ground. Do you have a surcingal and side reins? Confirm it with someone first, but maybe you could put a very gental bend on her and asking her so that she gets a clue. Of course each time you changed direction, you would have to adjust the reins, but it'd be worth it if you could getting her going correctly for awhile.
My boy Rebel use to do this too me. Hence his name however. What I had to do was right before you saw him try to pull or just as he started to was give a firm tug then release. Don't play tug-o-war with them, because you'll never win. Also, when they're pulling give an "AHHH AHHH" in a repremanding tone. Like I said, not too terribly hard, you don't want to knock them off balance, but just enough to get their attention.
What conditions are you lunging in? Large arena, small round pen, in the open? Does anyone ride her? Can you drive her? The more information, I think, the more people will be able to give you better advice!
Anyone whom see's my information as wrong, please correct it. These are just thoughts and suggestions.