Female dogs are in heat for around 21 days but sometimes it can go a bit longer,they can not be spayed while in season so you will have to wait and keep her away from intact males for (to be on the safe side)30 days at the least.Thank you for making a responsible decision in having her spayed!Congrats!
ETA:I forgot to mention that some vets will spay when a b*tch is in heat but most will not,you will need to call your vet and ask if you do not want to wait.
Some dogs can be in heat for more then 3 months. Dogs go through 4 stages while in heat. Most vets won't spay a dog while it's in heat because it can be very dangerous due to the excess bleeding.
Yes, you can get her fixed while she is in heat. Bravo to you for doing the right thing. You realize that the health of your little dog is more important than making a buck! Good pet owner! :)
I don't think you can while she's in heat. Too much blood in the female parts, and they are slower to heal. Ten days or so is usually the longest dogs stay in heat. Three pounds, huh? Boy, that is small. My dog's half Yorkie. Called a Silky terrier. Yorkie mixed with Australian terrier. Believe it or not, my dog kills poisonous snakes. He's really, really quick. I call him Fred. Don't try that at home with yours, please. Takes the Aussie in him to be that quick, and he's 10-1/2 lbs. Good luck with your girl.