It's because they are not pronounced the same. Japanese write words depending of their prononciation.
For example, they write "Heather" as "ヘザー" (Hezaa).
Most of the time, japanese often choose video game characters names without really thinking if it mean something, if it's awkward or not (same for animes, they often put english sentences in it, and most of the time, it become some engrish without a proper meaning).
Not to mention they sometimes do errors when they write english words with katakanas.
I don't know what is is, but what I'm sure is that's definitively not "Lisa/Lysa".
Could be "Isa" : http://ja.wikipedia.org/wiki/イーサ・タウン (Isa Town)
By the way, the japanese wikipedia says, when you type "イーサ" : エーテル(Ether)の英語読み (which means "English reading of Ether")
Which would mean "イーサ" is "Ether" but with another pronounciation (another language) ?
It's not french for sure, we also pronounce it "エーテル".
Maybe "Mizéris Lutz Isa Lanai" looks better.