Normally, Lovies need to be DNA sexed. My MoJo girl, RIP (girl in my sig), was DNA sexed with a blood sample. That's the only way I knew she was female. I still have her sexing certificate from HealthGene.
However, the colors of Lutino and Creamino in Lovies is a sex-linked trait, so you can know the sex based upon the coloring and the genetics.