Save Your Own by Elisabeth Brink
From Amazon description:
Meet Gillian Cormier-Brandenburg: a virginal, narcoleptic, atheistic Harvard Divinity School student struggling to finish her Ph.D. thesis. When her fellowship is revoked, Gillian must venture outside the walls of academia in search of a new source of income as well as interview subjects for her dissertation. She takes a job at Responsibility House, a halfway house for recovering addicts. Here pintsize Gillian is charged with the unlikely task of imposing order on unruly tenants, including motorcycle-obsessed Janet, impulsive former prostitute Florine, and self-righteous Stacy, who begin to inspire her to rethink her own dreams and desires.