I Have A Shitzu Who Is In Heat For The First Time, Help?

It usually takes about two-three weeks from the time the dripping starts to the time when they are no longer in heat. Yes it is very normal for the swelling to exist in the private area. It can sometimes be 2-3 times bigger than normal. As long as she can pee good still, she will be ok. It is possible for her to get spayed while they are in heat. I had my female rat terrier mix spayed while she was in heat, because I saw her tied up with a labrador and The last thing that I needed was some puppies that would kill her during birthing. Some vets will spay her without any extra charges. You will just have to call the vets in your area to see what the charges are to spay a dog and if it is extra if they are in heat.
I wish you luck.

I am hoping your 07 is a mistake and your pet hasn't been in heat for 15 months. There periods usually last about 2 weeks, getting less and less as the days go by. As far as the swelling, my pet never experienced that.
But if it is enough for you to notice and obviously be concerned about I would make an emergency visit and not wait around for her appointment. I hope everything is O.K.