It’s the usual way of forming the plurals of most nouns when they’re governed by possessive adjectives; it’s not special to éadaí. It’s also used in the same way with unquantifiable nouns, e.g. ár gcuid bainne (“our milk”).
It would be wrong with cuid when a plural noun is an inherent, solid part of something else; otherwise, it would be wrong without cuid. Two correct examples are a cuid méaracán (“her thimbles”) and a méara (“her fingers”).
I understand it's more like "portion" or "share", as in "her share of clothes"; the implication being "of all the clothes in the world, the portion that are hers". Something like that, at any rate. As scilling says above, very usual, not emphatic.