Naomi is one of the 2 main characters in this story (well, 3 really - Boaz is even more important than Naomi and Ruth in the prophetic implication of the book). Anyway, Naomi and her family left Canaan during a time of famine, but she returned from Maob without her husband or her children. She did however return with a very special daughter-in-law: Ruth.
Less noble is Orpah and Naomi in this narrative. Orpah (Naomi's other daughter-in-law) didn't have the same faith that Ruth had. When the offer to return to her people and to her gods was presented to her, she took it. Now, God's mercy toward Naomi was great... but did she fully appreciate it? Later she would indeed arrive at that higher plane of understanding and gratitude, but she wasn't there at this point in the narrative. Take notice of how she very nearly blamed God for her misery (Ruth 1:20-21)!