Eowyn's "disguise" - who was fooled by it?

[Rumil]

It seems plain that Elfhelm knew what was going on. I wonder if he secretly fancied Eowyn such that she could twist him round her little finger? Perhaps this is the great unrequited love story of Middle Earth!

I mean, who else would she be expected to marry (considering that in medieval times the bride didn't have too much of a choice)? Obviously not Eomer or Theodred, Grimbold and Gamling were too old, and as for Grima -yeeeuccch! That leaves only one prominent Rohir, namely Elfhelm. Of course, nobody could have expected her to fall for an unknown northern ranger or the prince of Gondor!