I was thinking for a bit, and I realized Lina's name is Lyuri in the Japanese version. The Japanese version came first, and therefore, your evidence is void!
Group: Arcs
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Joined: 5-June 10
Member No.: 2062
You can't take the English in the Japanese version as canon; Sting doesn't know English. Hell, the English transliteration doesn't even match up with the katakana used to spell her name.
But Ein's the protagonist anyway, so if anything only he's the main character--Cierra, Fia, and Lina aren't main characters either. They're just part of his possible-endings harem.
As is Ledah in the newest RiviPSP release, but that's besides the point.