You are mixing spelling of the name (transcription or transliteration) with figurated pronunciation. When transcripted to Western languages, the Arabic name is usually transcripted as Layla
pronounced ['lajla] (for your information, that is IPA, which is the only scientific way to represent pronunciations); the pronunciation ['lajla], when intended to be read in English is commonly represented LY-la or LY-lah. The Persian form is usually transcripted Leyla
, pronounced ['lejla], commonly represented in English figurated pronunciation as LY-la or LY-lah.