I received a letter from my landlords lawyer warning me of eviction if I do not remedy a breach in the lease. The tenant downstairs claims my girlfriend is permanently occuping the apt. w/ me. The lease states 1 occupant, my girlfriend has a set of keys and spends a significant amount of time here, she does not live her, there is no clause in the lease pertaining to the number of keys allowed per unit/occupant(the keys are not stamped "do not copy"), and there is no clause limiting the number of days a visitor can stay at the property. Before I pose an argument I need to find out if my actions breached my lease despite the fact that the accusations are not specifically mentioned. Thanks