No its not normall maybe take your puppy to the vet and tell them about it because the vet knows everything also I have 10 puppies of my own and they have never had swollen nipples
Some do, some will even lactate and must be monitored for infection like mastitis. She may be a little more prone to things like false pregnancy as well (hormones). Are you concerned some male may have gotten her? If there was an accident you can speak to the vet about the mismate shot and it's risks if it's soon enough after or a spay and termination. Do you have plans to spay her soon? You don't have to worry about any of the pain in the behinds and concerns of seasons (and risks of pregnancy) and they are healthier and live longer. If she just now seems to have gone out be sure to keep her away from all intact males 4 months and up for at least another 7 to 10 days and don't leave her alone or take her into public yet. Good Luck.