The boiling water tip works well. As you already have her head off, I would fill her with boiling water - repeat as the water cools and then when the plastic is soften gently manoeuvre her leg into position; hold it there with something soft [curlers or packed bubble wrap] and which will not stain or indent the plastic further. Then toss her in the freezer for a few days. Bring her back out and she should be fine.
You can substitute the warm water for a hair dryer directly on the leg if you prefer. And in very severe cases I have had to repeat this process a couple of times.