If your female is not spayed, then it would be normal for a heat cycle. The heat cycle lasts about 3 weeks. Sweilling normally starts the first week, with swelling increasing more the second week. At the end of the heat cycle, if the dog has not been breed, the vulva shrinks back down. Many times it seems like the vulva is smaller than normal after the heat cycle. Females that are spayed do sometimes develop a smaller vulva as a result. You can see some pictures of a female in heat here:
Hope this information is helpful to you.
Your original post stated "My female boxers vagina has been swollen since February 18th and now it is only half the size it was!! " which sounded like a female dog having a heat cycle and coming out of the heat cycle.
Your most recent post sounds like she is still extremely swollen and possibly even has vaginal prolapse which is when a portion of the vaginal wals protrude out of the vulva and it looks like either a ball, tongue or donut shaped piece of tissue hanging out.
A female dog in heat does tend to get huge and it seems to me that the smaller dogs tend to get even larger than the bigger dogs. However, each dog is different. The chi next door's vulva is normally about the size of a quarter but when she is in heat it is almost as large as a tennis ball it gets so huge and then shrinks back to normal at the end of the cycle. My rotties start slightly smaller than a tennis ball and go to the size of a softball and then back down. I have one that periodically doesn't swell at all which is referred to as silent heat.
During certain phases in a dog's heat cycle, vaginal tissue may swell and protrude through the vulva and look like a tongue shaped object. This is vaginal prolapse. This is seen most often in young intact female dogs. The breeds most commonly affected include the Labrador retriever, Chesapeake Bay retriever, boxer, English bulldog, mastiff, German shepherd, St. Bernard, Airedale, springer spaniel, walker hound and Weimaraner.Symptoms are a protrusion of a round tissue mass from the vulva, Licking of the vulva, painful urination and not allowing breeding. If your dog can still urinate, it is not generally an emergency, but your dog should see the vet as soon as possible. If your dog can not urinate, then it needs to see the Vet immediately. You can read about this here:http://www.petplace.com/dogs/uterine-prolapse-in-dogs/page1.aspx
If you have further questions, be sure and hit reply and let me know your concerns. Here are some pictures of a vaginal prolapse.
That is exactly what it is!!! Thank You!!