I believe the tenant that moved out has broken the lease. My understanding is the domestic violence laws only apply to "roommates" if they are in a sexual relationship. You can't just end a lease. However, you need to mitigate your damages. Is the other roommate still in the property? If yes, then both roommates (assuming no sexual relationship) are responsible for the rent (no requirement to live in the property) and the security deposit will be returned when the unit becomes vacant.
2016 Maryland Code
Title 8 - Landlord and Tenant
Subtitle 5A - Rental Housing -- Victims of Domestic Violence and Sexual Assault
§ 8-5A-03. Notice -- Victim of domestic violence
Universal Citation: MD Real Prop Code § 8-5A-03 (2016)
(a) Delivery. -- If a tenant or legal occupant is a victim of domestic violence, the tenant may terminate the tenant's future liability under a residential lease under § 8-5A-02 of this subtitle if the tenant provides the landlord with written notice by first-class mail or hand delivery of an intent to vacate the premises and notice of the tenant's or legal occupant's status as a victim of domestic violence.
(b) Copy of protective order. -- The notice provided under subsection (a) of this section shall include a copy of a protective order issued for the benefit of the tenant or legal occupant under § 4-506 of the Family Law Article. --108.56.xxx.xx