Nice, also immortal, wife of the grumpy immortal dude. She bakes bread and urges Utanapishtim to tell Gilgamesh about the plant that makes you young again.
Utanapishtim's wife has a small role in the story, but it's an important one. Basically she provides an antidote to her husband, who comes across as a bit of a smug jerk. From Utanapishtim's story of the Flood, we learn that he and his wife were granted immortality by the god Enlil after they survived the deluge that destroyed most of the human race.
When we meet Mrs. Utanapishtim, she is living with her husband in a secluded location in the underworld—not exactly a happening place. She first makes her presence felt in an important way after Utanapishtim has challenged Gilgamesh to stay awake for six days and seven nights. Of course, Gilgamesh, who has just traveled the furthest distance that any human being has ever traveled, immediately falls asleep. Seeing this, Utanapishtim begins making fun of him; this is when his wife steps in to scold him for being so immature.
All the same, she does comply with his request that she bake a loaf of bread for every day that Gilgamesh is conked out; that way, when he wakes up, there will be proof that he really was asleep for that long.
When Utanapishtim sends Gilgamesh away in disgrace, Utanapishtim's wife shows her good nature again when she insists that her husband call Gilgamesh back and give him something for his troubles. This is what prompts Utanapishtim to reveal the secret of the flower that returns the youth of whoever eats it.
All in all, Utanapishtim's wife seems like a nice lady. Too bad she's married to that jerk.