Flea dirt around nipples?

She is a 20 month old seemingly very healthy happy cat. There is a very good chance she's pregnant. I noticed her nipples we starting to get bigger a few weeks ago and today when I rubbed her belly I felt something crusty. Her nipples are getting crusty, which being a mom myself I understand could be a normal sign of lactating. The thing that's concerning me is most of her nipples have brownish spots around them. I've read that it could be from flea's. She did have a major flea episode a couple of months ago but she's in her second month of being treated with "Bayer Advantage II" flea treatment for cats over 9 pounds.
Is it possible this is from the old flea bites or could it be something else? She doesn't show any signs of having fleas now and my daughter has no new bites.(they sleep together at night). She had all her shots when she was a kitten, but I don't take either of the cats to the vet unless something is wrong because I have Multiple Sclerosis and my only income is Social Security disability. I can send you picture if you need me to.
Thank you for any help you can give me.

I sent you 2 picture one of one of her nipples and one of her, as you will see her coat looks fine, I'm just worried about her nipples, I can't find the black dots anywhere else on her body. As far as using the flea treatment, she went into heat after her last treatment, but I'll get the other treatment for her for now. Thanks again for your help.

Thank you very much. She has shown no signs of it bothering her at all. I found you during an internet search and decided the investment to ask the question worth it when I looked over your website. My gut told me she was ok, but she's by baby's baby and I just couldn't afford a vet visit right now. If I had to I'd borrow the money from my sister. You pretty much confirmed what my instincts were telling me and for that I'm grateful. Take care : )