The mother of Gilgamesh. And, for heaven's sake, don't take parenting advice from this gal.
Gilgamesh's father, Lugalbanda, was a mortal human, dead before the beginning of the epic. Much like Thetis, the goddess mother of Achilles in Homer's Greek epic The Iliad, Ninsun is extremely devoted to her mortal son Gilgamesh, and is always trying to help him out. We can see her helpful nature when she puts in the good word for him with Shamash, the sun-god, before he and Enkidu set out on their quest to fight Humbaba. As it turns out, they need Shamash's help to defeat Humbaba, so Ninsun has an important effect by acting as a go-between.
But Ninsun isn't just well-connected. She also has deep insight into her son's personality. For example, according to Shamhat's account at the end of Tablet 1, when Gilgamesh has a pair of disturbing dreams involving a mysterious meteorite and an axe, each of which he embraces "as a wife," Ninsun interprets this as meaning that Gilgamesh will be getting a friend.
This comforts Gilgamesh, and might pave the way for him becoming buds with Enkidu, even though they fight each other the first time they meet. From such small, thoughtful acts as these, we can get a good sense of Ninsun's maternal, caring character, despite her small role in the epic.
We also think it is important to note that Ninsun may be Gilgamesh's mother, but that doesn't keep the narrator from commenting on her role as woman: when she goes to pray to Shamash she wears "a robe worthy of her body" and "jewels worthy of her chest" (3.39-40). In other words, we can assume that Ninsun is a hottie—even if she is someone's mom.