Susan,
I actually said 'at least one version' meaning I hadn't checked all the references thoroughly. Looking more closely the two pieces I printed off are the same ballad but posted at different times, both of them to Horace Walpole. One has been simply scanned so there are typos.

If by the Campbell version you mean Child E it is pretty obvious to me this corrupt version is derived ultimately from Child A or a version thereof. As someone has already stated the rose-briar motif is so widespread internationally in ballads and elsewhere to draw any hard and fast conclusions about precedence. It is quite possible that some of the English language ballads picked it up from separate translations of different continental ballads. It would to take a pretty exhaustive study to determine this of course.

Personally I think you're reading far too much into these versions. I will take a lot more convincing and the aesthetic value of any of these doesn't tell us much in scholarly terms.