I have a precious 9 & 1/2 month old female daschund. She started her first heat cycle last Wednesday. I have set up an appointment to have her spayed during the first week of July. She's experiencing ordinary symptoms, including swelling. However, she has swelled up nearly three times her usual size. Is this normal? When does swelling normally begin to dissipate? She doesn't show any signs of being in pain and remains completely active.

A dogs heat lasts for 21 days.
During this time she should not be allowed near any male dogs, it would be very dangerous for her to become pregnant at this age.

The swelling is normal, some only swell a little, others swell a LOT. The only thing to watch out for is any unusual colored discharge (green, yellow etc) as it can be a sign of infection.

Keep your lawns extra short during this time as when they squat to wee it is easier for them to pick up infection from the grass, and by making it shorter you reduce contact.