One basketball player at Boston University said she felt so emotionally damaged by her coach she considered suicide. Another player said the coach, Kelly Greenberg, treated her so poorly she sought mental health care. And two other players said Greenberg’s emotional abuse ruined their love of the sport. All four women walked away from the BU women’s basketball team this academic year, an exodus that has renewed questions about Greenberg’s treatment of her student-athletes — and her future at the school.