I've been dabbling the last few days in scholarship on Cistercian nuns, particularly on the topic of whether there were Cistercian nuns. Well, yes, there were, but the question is when they were, and how nuns became attached to the order.
The traditional narrative holds that the early Cistercians distanced themselves from women, except for a few leaders such as Stephen Harding and Bernard of Clairvaux who offered spiritual advice to religious women only informally. Then in the late 12th century, the clamor of women seeking places in monasteries, combined with other pressure, forced the Cistercian General Chapter reluctantly to admit houses of women to the order.
Probably the primary voice arguing against this narrative in Constance Berman's. In "Were There Twelfth-Century Cistercian Nuns?" (Church History 68:4, Dec. 1999, pp. 824-864) she attacks the question head-on, and connects it to her larger attacks on the traditional narrative of Cistercian origins found in The Cistercian Evolution. Berman's position is that the 12th-century expansion of the Cistercian order happened through groups of reforming hermits & monastics taking up Cistercian customs, and gradually being incorporated into the developing order (rather than new houses being seeded, so to speak, directly from Citeaux and Clairvaux). She further argues that many of these reforming groups included women, that such women viewed themselves as Cistercians, and that historians have applied overly rigid and anachronistic standards to dismiss many women's houses as only "imitating" Cistercians. She generally argues that, where local records of a house having Cistercian customs conflict with the order's narrative sources, the local records should be trusted, because she considers the dating of the narratives to be highly questionable.
Now, Berman has her share of critics on these issues, but the material I am looking at inclines me toward her approach. I'm looking at material related to a Catalan nunnery (Santa Maria de Vallbona) which is presented as unambiguously Cistercian in the local historiography. Catalan historians often seem to blithely ignore historiographical debates focused on other regions--in fact no Catalan article related to Vallbona appears to cite any of this controversy, or the traditional narrative. But they do know their local sources quite well. In fact, the foundation story that appears in the multiple histories of Vallbona I've looked at fits Berman's pattern beautifully:
A charismatic hermit called Ramon settled down in the Good Valley of Vallbona, attracting a number of followers, both male and female. After some time the group decided to adopt a more formal set of customs and separated, the men perhaps joining the community of Poblet. The women invited a nun from the Navarrese Cistercian community of Tulebras to come and bring them Cistercian customs, which she did c. 1175. That is not super-early in the Cistercian chronology, but it is earlier than when the General Chapter is supposed to have been pressured to admit women. It's a little earlier than the foundation of Las Huelgas in Castile. I do think, based on the local accounts and sources, that Vallbona was Cistercian. Its material seems unfairly obscure, though; it's seldom cited in studies of Las Huelgas, much less related to developments in France. Unfortunate, as it could provide useful counterpoint.