[EBN] [GTW] Half-Aliens Can't plant fairy seedling

Is this a glitch.  Tiara's mother was a green alien as was her mother. Tiara inherited her mother's green alien skin, but she is not alien. I wanted to turn her and her husband into fairies. As soon as Junior, Tiara's husband, planted his seedling, Mother Nature showed up and he became a fairy.  When she tried to do the same, the option was not available. She was pregnant at the time, so I thought maybe that was the problem. I had her try again after her daughter was born but it's the same as before. Does anyone know if sims with alien skin tone cannot become fairies?