My 10 month old little Jilly Bean is in heat!!! OMG

I didn't even notice it until the night they were going to the Petsitter. But looking back now there were signs. I should have known. I do have a question. Is is typical for them to loose a little weight when they are in season. We had noticed and so did our groomer that she appeared to be a little on the boney side. I weighed her and she did loose about 4 oz. She weighs 3 lb. 5 oz. now. For such a little thing, she does have a discharge. I was prepared with a doggy diaper which she is not thrilled about wearing. Can someone refresh my memory on the length of time the discharge will last. I had a female dog many years ago.
We are planning to get her spayed but decided to wait a bit until more of her teeth fall out. Our vet was okay with this especially being so small. After reading some posts on YT, I was perfectly comfortable waiting as well knowing full well she may come into season while we waited.