The Emerald Wiccan

She is an Emerald. Her job is to find the young humans just coming into their magic and get them off earth as fast as possible. She sees all the signs of a youth feeling the first flush, but can't find the budding witch or warlock. She must get to them before the others find and kill the human. She locates a somewhat nerdy professor, but not the person she seeks. It's not fair to a human to allow anything to develop between them.
When she discovers the full-grown man is the person she hopes to aid, she takes him home. But things have turned nasty on her world. Those who hate anyone not of the proper standing want to destroy him and she could be collateral damage physically and emotionally.