The cover depicting the first appearance of the Legion's first Real American hero (SUPERBOY #226, 1977) is a pretty typical "dump on the new girl (or girl)" schtick.
I reread a handful of Dawnstar's early appearances, and my knee-jerk opinion is that her creator Paul Levitz didn't seem to have much of a story-arc for her, aside from making her the girlfriend to the already established Legion member Wildfire. It may be that Levitz had nothing more in mind than countering the "whitebread" look of the 1970s Legion, for Dawnstar's costume design is largely her best feature. She and her people, Earth-bred Amerindians who were transported to another planet and used in a bio-engineering experiment, hence the wings. In her first appearance she's said to be a mutant, though the later origin suggests that all the powers she possesses are held in common by her people. Her most stereotypical power, as far as her being Native American, is that she can track enemies across the depths of space.
At the time of her appearance, I thought she was largely a feeble attempt by DC to emulate Marvel's mystical-seeming Storm, who had debuted about two years previous. Here's a blogpost that cites some if not all of her major story-arcs; apparently she's no longer a member of whatever Legion exists today.