Canine lactation

Question
Dear Dr Connell,
I have a 7-8lb mini-pinscer/chihuahua mix rescued dog, who is approx. 7 years old, she was rescued from a busy highway by a friend, who has since passed.
I have had my girl for almost 5 years now, when my friend rescued her from traffic she was still a VERY young, VERY tny puppy.  She has never been bred since my friend found her (I'd have had her spayed, but she has an umbilical hernia, and the only places that do low-cost spaying in my area won't do it because of the hernia.)
My girl has begun lactating in the last week.  I'm told this is not uncommon for females who are around newborns, which my girl isn't.  (No baby critters of any species in her surroundings.)
So, my questions are: #1.  Is this cause for concern?
And #2. Does lactation indicate that she has had puppies at some point? People have suggested to me that she might have been bred, I didn't buy it because she was so young when my friend rescued her, but I've heard that puppy mills start them breeding as early as physically possible.

Thank you for your attention.  I'm sorry this is so ling, have never mastered the art of brevity when writing.

Answer
First of all, you are not really sure this is milk coming out of her nipples are you? Is it all of her nipples or just one or two?

The reason I ask is that dogs at this age that have not been spayed are usually going to get breast cancer because of having not been spayed.

Many times the tumors they get look like the teats are swollen and they will ooze liquid. This doesn't mean that she is lactating.
Spaying a dog at this age helps some, but won't stop the cancer now. The only thing that can be done is to have them removed but they usually come back.

She would not be lactating now regardless if she was bred before you found her or not. She would be having a false pregnancy if she was truly lactating and showing signs of that such as nesting, hiding, even bleeding vaginally and all of her teats would be swollen and soft.

You need to get this dog to the vets and have her looked at soon. If she does have breast cancer, or mammary tumors, then the sooner you get them removed the better her chances are.

I have never heard a vet not spaying a dog due to a hernia as that is the best time to repair them. I don't understand the puppy mill connection here at all.

Call your vet and have her seen this week. You need to get on this quickly.