Having her fixed will solve this issue. But don't wait, every heat cycle she has will increase her chances of cancer and other reproductive health problems.
Yes it is possible for any female dog in heat to have swollen gentials. Sometimes dog's nipples even swell. It seems to be just signs the dog is in heat.
Yes it is. This is the just one of many stages of heat a female will go through. Depending on which stage she is in I am assuming the 2-3 week. Swollen genitals is very normal.