It was only on my somethingth re-read of The Lady of the Fountain that I realised Luned and the Lady are described with the same features and clothes (except Luned wears a frontlet of gold).
This is when Owain is trapped by the portcullis and sees Luned:
And later when he sees the Lady:
So Owain looks out the window and falls instantly in love with a woman who looks identical to his bestie. Yes, I’m convinced they knew each other and were friends before all this, not just because of the way they talk to each other but also later we have this:
I’m already feeling totally normal about all this so I go and look up the meaning of Luned’s name because I also think it’s very very interesting we have her name but not the Lady’s. Seems like it’s derived from ‘Eluned’ meaning ‘image, likeness, idol’ - not a coincidence that these two women look almost identical, then?
So if we’re meant to notice all the similarities, the one difference stands out and begs the question: why does Luned, the handmaiden, wear a gold frontlet on her head, but not the Lady?
My definitely-very-normal-about-all-this headcanon is that Luned was in fact (unhappily or perhaps unwillingly) the Lady of the Fountain, and when she heard her husband had been defeated tried to escape, which is why she was by the exit when she came across Owain. She had left her identical looking handmaiden in her place hoping nobody would notice, but forgot to give her the frontlet.