[name]Violet[/name] [name]Opal[/name]: I love both names but not together, because I think of a purple colored opal.
[name]Violet[/name] [name]Louise[/name]: I love both names, but when I say them out loud, the L’s trip me up, making it sound very L heavy. What about [name]Louisa[/name] [name]Violet[/name]?
[name]Violet[/name] [name]Kate[/name]: I love both names, but because both end in a T sound, I think it sounds a bit harsh when I say it out loud. I love [name]Violet[/name] [name]Katherine[/name] and though!
[name]Violet[/name] [name]Frances[/name]- I think this is beautiful! 
[name]Edith[/name] “[name]Edie[/name]” [name]Rose[/name]: [name]Edith[/name] has really been growing on me lately…
[name]Opal[/name] [name]Elisabeth[/name]: Because of the Ls in both names, [name]Opal[/name] [name]Elisabeth[/name] is hard for me to say out loud.
[name]Opal[/name] [name]Elsie[/name]- Ditto.
From your list, I think that [name]Violet[/name] [name]Frances[/name] and [name]Edith[/name] [name]Rose[/name] have the best flow, so I’m voting for those combos.
Good luck!