Lasair, Latiaran, and Inghean Bhuidhe?

oh wow this is a fascinating find! lasair sounds really familiar, maybe because of the saint? i wish i could provide more concrete info for you :\ hopefully someone else can or something will show up! good luck and def share anything you find with us, i know i'd love to hear more!

Okay, so updates on what I've found:
Roles of the Northern Goddess by Dr. Hilda Ellis Davidson mention the trio, briefly. I quote it below, in it's entirety, because I'm weird like that.

"At Cullen in County Cork, Lughnasa was celebrated on Latiaran Sunday, the Sunday on or before 25 July, the day of St. Latiaran, their patron saint. She was remembered only in popular local tradition, and said to be the youngest but most important of three sisters, the two elder were called Lasair (Flame) and Inghean Bhuidhe (the Yellow-Haired Girl), but the meaning of Latiaran is not known. Lasair and Inghean Bhuidhe had sacred wells, but Lasair's had been earthed over by order of the MacCarthys when they were chieftains; after a plow had been placed on top; this was said to have brought bad luck to the district. Latiaran's day was the beginning of the harvest and Inghean Bhuidhe's on 6 May, at the beginning of summer, so that Lasair's might have been the beginning of spring, (MacNeil 1962: 270-1) which would explain her association with a plough."

The Encyclopedia of Celtic Mythology and Folklore by Patricia Monaghan mentions them as well, but suggests that Latiaran and Lasair are the same, and that Latiaran is merely a corruption or dimunitive of Lasair. She then goes on to say that they may both be variant of the "great figure of Brigit." Which makes me side-eye her entry a LOT.

Sometimes I think people want to equate all Celtic goddesses with either Brigid, Na Morrígna, or Danu (WHO I STILL HOLD DOESN'T EXIST).

I signed up for a trial at JSTOR or whatever, and have two weeks to read The Life of St. Lasair by Lucius Gwynn and David O'Duigenan
Which was published in a journal called Ériu in 1911. (I didn't know journals existed then, go figure.)

I did some more research about St. Latiaran as well, and found she's referred to as both St. Latiaran of Cullen and St. Latiaran of Cuillin, which is a place...on the Isle of Skye, where Scáthach trained and lived, and gave her name to as well. Cuillin itself may have been named after Cú Chulainn, who trained there with Scáthach, which makes me wonder if some people may have thought Latiaran was the daughter of Cú Chulainn, and the etymology got corrupted somehow. It's kind of a weird theory, I know, especially since the three's father is supposed to be a man named Douglas, but I wonder none the less.

I still want to get a hold of Máire MacNeill's "The Festival of Lughnasa" that Dr. Hilda Ellis Davidson cited. I haven't been able to find it yet.