From the context, the time sounds like somewhere between the 16th and 18th centuries; Dónal is clearly living as a woodkerne, on his keeping in the forests - "it is you are the lonely bird through the woods"; he is also clearly a man of some wealth and power, whether this still exists for him or not, since he's able to promise the speaker "twelve towns with a market in all of them, and a fine white court by the side of the sea… and a suit of the dearest silk in Ireland" as well as the less realistic offers of things that appear in the traditional mystery tales: a ship of gold under a silver mast, gloves of the skin of a fish, shoes of the skin of a bird.
The woman who's speaking (or man, of course) is not rich: "it is I would be better to you than a high, proud, spendthrift lady". Not only would s/he milk the cow, but also - again suggesting that he's living as a woodkerne - "I would bring help to you; and if you were hard pressed, I would strike a blow for you".