Is Kinana relevant in the manga? I may not remember very well, but I think it was after the Edoras Arc that Kinana makes her first appearance in the anime as a maid within the guild.

We know for a fact that she was previously Cubelios, Oracion Seis Cobra's partner.

Her only relevance as Kinana in the anime was to hear him at the end of the filler arc (anime only) including the "New Oracion Seis" and I think she reappeared again at the end of the Dragon King's Festival for the same purpose (poor girl).

And as I don't remember very well how things turned out in the manga at the end of that same arc, my question is 

Did she serve any purpose at all in the manga as Kinana?
Simply no. You don't even see her in fights. Such a shame really.