Mast means, breast/udder
Itis means, inflammation of
So

it this is a teat wound infection, no she does not have mastitis. I would however get her up on a milkstand or have someone who knows a little about goats, really look this does udder. You definently want to deal with this problem now while she is dry and not wait until she kids.
They make cannulas that you can insert into the teat to keep it open, these are medicated. They make infusions that you can purchase for dry cows, that you can insert partially and squish this medication into the teat to help heal it. At the same time you will likely want to put her on injections of penicillin.
But until we get more information, which means temp, what's the teat really look like. What happens when you milk it. Is the white fluid coming from the udder or the teat? Is the udder warm, is there fluid in it, in each side? Do you feel lumps inside the udder or teat?
Of course you would never want to put an animal with an undiagnosed problem in with your other stock.
Worse case scenerio is that this is a CL abscess that has burst in her udder, the exude is infecting not only your other stock but your place. Vicki