Her role could initially be that of a liability. Since she's suicidal, she might not be fully committed to the team's goals at the start. However, as the story progresses, she could become the team's emotional core. She has experienced so much pain that she has a deep understanding of emotions. This could help her in situations where the team needs to understand the motives of an enemy or deal with a civilian in distress. For example, if they encounter a group of villagers who are afraid because of an attack, she could relate to their fear and be able to calm them down better than the others in Team 7.
She might be the one who challenges the status quo within Team 7. Her different mindset due to her suicidal thoughts could make her question the traditional ways of doing things in the team. This could lead to new strategies and ways of thinking. For instance, she might suggest a more unorthodox approach to a mission that at first the others are skeptical about but then turns out to be very effective. Also, she could be the one who forces the team to confront difficult topics like death and sacrifice more directly, which in turn makes them stronger as a unit.