Well, unfortunately I'm not an expert like Cleveland or... other experts on this board. (My specialty's Old English and Germanic names.)
However, it does occur to me that your wife's name could be a mutation of Zelda. Alternately, your parents-in-law could've made it up, composing it from random sounds they thought sounded pretty. If it's the former case, your wife's name means either "grey battle" in Germanic or "luck" in Yiddish. If it's the latter case, then I'm sorry to say that the name has no etymological meaning.
But I emphasise that you shouldn't take my word as gospel here. You should wait to see if maybe someone else with more authority will come along with more info. :-)
Proud adopter of 15 punctuation marks; see my profile for their names.