I'm not sure what they were trying to say in that scene, but these theories are as good as anything I've come up with. I definitely DID think they were supposed to be sisters, though.
I really wish they hadn't bothered with the downstairs plot overall. I agree with the person upthread who suggested the time would have been better spent with her ladies-in-waiting. That's a position I've never really seen explored, as opposed to the servant angle, which was so fully brought to light in Downton and in Upstairs, Downstairs before that. I don't even know her ladies' names, there's just the one who looks like Laura Benanti and does all the talking, and some other people. They're all brunette, too, which doesn't help!
I bought Victoria and Albert's chemistry, and I'm glad the "romance" with Melbourne is over, as much as I like Rufus Sewell. The only other thing I've seen Tom Hughes in is Silk, where he didn't get much to do, so he's a clean slate for me. He's a little intense and quiet, but I thought it was a nice contrast to everyone else who are constantly blathering nonsense. Everyone thinking they should get married based on one piano duet! So silly.
I have a new favorite word: Waldeinsamkeit.