This is new to me. I'm saying "uh-LESS-ee-uh and guessing that's correct since it's related to Alexis. I'm enjoying the softness of the short "e" and the double "s". I would hope people wouldn't assume it to be a creative spelling of Alicia/Alecia. They shouldn't since, generally in English, a double consonant makes the vowel preceding short. Ideas...hmmm...
Alessia Gwen
Alessia Gwyneth
Alessia Constance
Alessia Helen
Alessia Joanne
Alessia Maeve
Alessia Kate
Alessia Joy
Alessia Fern
Alessia Pearl
Alessia Wendy