> Has the lady been put under a spell?

That seems to be the implication in some of the Scottish versions in Child (A, B, C, D, F) where they "cast their glamour o'er her" etc. According to the Dictionary of the Scots Language (http://www.dsl.ac.uk), glamour = "Magic, enchantment, witchcraft; a spell, esp. one affecting the sight, as in phr. to cast (the) [glamour] ower someone('s een)". On the other hand the mondegreen in Child G ("They called their grandmother over") might suggest that already in the 18 century not everyone got the meaning, at least outside Scotland. "Charmed" could also mean there was magic involved, but it doesn't have to. According to the Shorter Oxford English Dictionary, the non-magical meaning of "charm" as "powerfully attract, fascinate" also goes back to Middle English.

> Can we assume that if we agree that the lady has been put under a spell that the choices she makes are no longer her own?

Maybe that one should be left for the lawyers, but poetically speaking I think it makes more sense if we assume that their magic (real or metaphorical) couldn't have such an effect on her if she wasn't already open to the possibility of running away. Child B has an interesting ending from this point of view: she declares herself free of the Gypsies' influence, but still won't go back to her husband.