I like it as EL-in, though pronunciation issues mean I prefer
Ellen. I would pronounce both
Ellen and
Elin EL-in. I've never met an
Ellen who said EL-ən.
I don't care for AY-lin much. It sounds like a tryndee creation (Ailynn or something) and is not very intuitive from
Elin.
Ellen/Elin is fairly dated here but I think it would be delightfully refreshing on a little girl. I'd be a bit sad if she became one of ten zillion little girls called
Ella or
Ellie, though.