Semi-wild cat w/kittens

We have a cat that is approx 1 1/2 yrs old. When she came to us, she was wild.
She is still not tame but she does tolerate us petting her when she feels
like it and feeding her. She is an outside cat, WILL NOT come into the house
no matter what you offer her. She had kittens approx 8-9 wks ago. At first we
thought that there were no viable kittens as it did not seem she was nursing
and we could not find evidence of any kittens. After about 4 wks, we noticed
that one side of her stomach (around her teats) was lumpy and a little
swollen. That is still going on and have now noticed hair loss around the
teats. She also does not seem to be putting any weight on. We have seen 1
possibly 2 kittens in the last day or so that we think are hers. I don;t know
if any of this is normal since we have never had a cat before. I would love
to take her to the vet but she only comes around in the late evening or at
night and even then you can't set you watch by it. She just kinds shows up
when she wants to. If anyone has any info or advice at all, I would really
appreciate it.