It's definitely fun to say! I'm not sure if there's a spelling I'd really like though. Katelaine is fine, so is Catelaine. Idk about Catelane.
It definitely looks like
Kat +
Elaine but there are so many names like Katelina,
Katarina, etc. that it blends well and doesn't look like a hybrid.
(This also made me look up "
Madelaine", which is apparently a real variant of
Madeleine. But I don't know if they pronounce the "ai" like
Elaine or like
Ai.)