Martin, I looked in Vallely's Companion, and I'd agree with you that it does have a lot of articles about individual musicians such as Lucy Farr, Bess Cronin, Róise na nAmhrán, Maggie Murphy, Julia Clifford amongst others. However there is no entry for "women" between wire recording and wood block, nor does the extensive bibliography appear to include any indications of previous studies in this area. I would imagine that somebody somewhere has done or is doing some research that would be helpful, but as far as I can see this is new territory, so eaferguson here is your opportunity!

It would be very interesting to discover how women such as Sarah Makem, and Sarah and Rita Keane, have contributed to preserving the Irish tradition - and to find out how far back in time this goes.

UCD has a women's studies programme UCD: WERRC and I think that Angela de Burca has done some folklore research which could be of interest (off topic do read her book The Burning of Bridget Cleary).