Swollen and growing nipples on spayed cat

My cat was spayed almost 2 weeks ago, she was also very early in a pregnancy. Since she has been spayed her nipples have been growing. Is that normal? Could it be hormones?

It may or may not be normal. 

It may be normal not as hormonal changes (those should have been eliminated with the spay and it has been long enough that you should be seeing a decrease in size if it was hormonal) but as a normal reaction to an abdominal surgery. Some people and animals can get swellings in the immediate area as a normal part of healing; which could appear to be swelling around the nipple and is just coincidental to the region. Depending on where the sutures are and the internal sutures it could be normal swelling as a reaction to those (I fall in the category of people who get bumps around sutures including internal ones). 

It may not be normal because it could be something unrelated but coincidental to the spay. It could also be an infection from the spay that she is developing. If you notice any redness, pain, drainage, vomiting, lethargic behavior, or refusing to eat take her in immediately (she is far enough out from the spay that she shouldn't be having any of those as a normal reaction anymore). I would also add if the lumps feel soft, hot or malleable that is an indication that there is a growing infection or pus and she needs a vet. 

The best course of action is to take her to the vet for a follow-up exam so the vet can see if it falls in the category of normal recovery. A vet check-up also creates a paper trail and makes your vet aware of it and noted as it is in case it spreads or grows.