I think Lilith is a pretty name. It ends with a "th" without sounding like s lisp. If the name existed, Lilis would also be pretty I suppose. I have gotten over hearing a lisp in my head when I think about the name Aerith. It can happen. Though I do prefer Aeris in a straight on comparison without any of the context and reasons behind Aerith being what it is. It reminds me, and reminded me the of Teiris from Dragon Force. A game I spent dozens of hours with. And even now if I think about the possibility of the name Teirith, I don't think its a horrible lispy derivative