Your dog may have vaginitis, or could be anal gland issues. It will be best to get the problem treated, and then she'll quit scooting on the floor/ground and licking. I would get her seen tomorrow. Expect them to possibly want a urine sample and don't let her urinate outside on the way in to see the vet. If it's urinary or vaginitis, she'll get antibiotics by mouth that will stop the itchiness/burning. If it's anal glands, they will express them and hopefully make the problem go away.
She might have worms or thrush. The vet is your best guide.
You can use a little vaseline but there's a reason why it's red, like an infection. Please have it checked out very soon, they are worth it and they depend on you for their care. Dogs=Love
