I'm sorry to hear this. Poor Beanie, I can't imagine how bad her paw must hurt. I'm sure it will heal in no time and she'll be running around and playing.
A couple of things. Did the vet give you pain meds for her. Please be sure to give them to her as prescribed. These little guys are very tough and brave and we often don't realize that they really are in pain. There is no reason to let them be in pain, it doesn't help them heal any faster. So please be sure to follow your vets instructions on the pain meds. And, of course, the antibiotics. Those are very important.
Also, if you have a Petco or Petsmart or other pet store close by, go and look for a soft cone for her to wear. There are several different styles and you'll both be much happier in the long run. This is one I have and my crew wear it with little difficulity.
ProCollar Premium Inflatable Protective Collar at PETCO
And PLEASE find a way to restrain her in the car. There are so very many things that can happen to them. As bad as you feel hearing her complain about the car seat it is nothing to how bad you'll feel if she is seriously injured or killed because she wasn't.