Nipple Question :D

So, goofy subject aside, I have a question about nipples.

We have a female cat that we adopted 1.5 years ago.  At the time we adopted her we were told she was 3 months old.  We were also told she had been spayed / fixed.

We have a male cat, also adopted, and neutered, we were told, he is about 2.5 years old.

Our vet has seen both cats multiple times and I assume has confirmed they are both fixed - it's never been commented upon.

Both are indoor cats and never go outside nor have ever been outside.  They play together every day, and at times I notice the male being sexually aggressive (biting her scruff and positioning himself over and behind her) but she doesn't seem to care and usually just lays there or eventually rolls over and bats him away. 

Within the past two months, I began noticing the female had visible nipples.  She has white fur and pink skin (she's calico) so I didn't think much of it.  I assumed she was simply "growing" into a mature cat and therefore her nipples were larger, too.  The most noticeable ones are the lower ones.  When she rolls onto her back they are quite clear.  I can easily see them from some feet away.  When I have felt them, they seem normal, she doesn't seem to mind them being touched when we pet her belly - so I don't believe there is any pain or swelling happening.

Her weight has not changed.  She eats normally and plays.  She has not been ill.  I don't see evidence of any additional tissue growth around them.  They just seem larger and bigger.  A pregnancy would have required divine intervention.

Is this normal for a female cat as they age beyond 1-2 years?  Do the nipples simply grow more obvious?  Could it be a reaction to the male's aggression?  Like a physiological thing - I have read some people who say a female can experience a false pregnancy but would this be true even if she is fixed?

Can you post a pic?

She is sleeping in her cat tree in a dark part of the house right now - I will try to snap a pic and upload it tomorrow when there is good light.  It's most obvious when she's laying in the sun (of course.) 

In the meantime here they both are ... up to no good!

Is she spayed?

My girl likes to get all sexual-like with my two younger boys. The boys were neutered in August and she was neutered last month, so I am 100% certain they are all fixed. Yet she still gets like that with them. They have no clue what she's doing because they never got to the point where they had raging hormones (neutered at 13 weeks). My girl however had a litter of kittens back in July, so she's obviously experienced raging hormones.

That is weird about the nipples though. Have you taken her to the vet by chance to get her checked out? I remember we had a cat back when we lived in the city (that was not spayed) that even the vet thought was pregnant after doing an x-ray. She even had been pulling hair away from her nipples, which had grown. Turned out to be pyometria. Unfortunately, I don't think there is any external way for the vet to tell with 100% certainty that a cat has been spayed. Of course, you probably would have known if she went into heat!

Did she have a shaved tummy when you got her? At 3 months, you should have been able to still see where she was shaved, because the earliest they can be spayed is 2 months, and it takes longer than a month for the fur to grow back. Although if she wasn't spayed she should have gone into heat by now. They can also have a bit of ovarian tissue missed and still go into heat. . .but again, that should have been pretty obvious by now. It could just be normal but if they get bigger let the vet know---some hormonal problems could cause teat enlargement.