San Francisco = Rent Control. (collective moan) to evict under a rent control jurisdiction requires that the tenant violate one or more of the issues set forth in Rent Control Ordinance. Section 37.10 provides just cause for evicting a tenant where "Tenant is creating a nuisance and disturbing other tenants or damaging property." From your fact pattern you appear to have just cause. Find someone who does nothing but tenant law in San Francisco. these firms typically do not charge hourly, but rather, on a flat fee basis. Be wary of anyone who wants to charge an hourly fee for this type of work.
A proper response would require a thorough investigation into the history and background of this relationship. The information provided above is just that, information, to be used as you see fit.