Complex sentence: Kelly's mother was Philadelphia native Margaret Katherine Majer (1898--1990), the daughter of German immigrants, who had taught physical education at the University of Pennsylvania, where she had been the first female to coach women's athletics at the institution.
Split into simpler sentences: Kelly's mother was Philadelphia native Margaret Katherine Majer (1898--1990) and the daughter of German immigrants. Margaret had taught physical education at the University of Pennsylvania, where she had been the first female to coach women's athletics at the institution.