I don't know the TORCA code on that particular detail but I seriously doubt that the Santa Monica Rent Control Board would countenance evicting a widow because she wasn't signatory to the original rental contract. Most rental agreements include clauses about the number of occupants and I'm pretty sure that it's the occupancy, not the signature on the rental agreement, that would govern the tenant's status.

Does TORCA apply to all members who live in the property or only to the member who signs the contract? Let's say a couple with a child is renting the unit. The husband signed the contract. The couple grows old and husband eventually goes to heaven. Can we then ask the wife to move out?

The most important part of TORCA left standing after various court decisions is that a tenant in a TORCA unit can not be evicted when an owner buys the property, even if the Buyer wants to owner-occupy. Other parts of the TORCA law, such as that you couldn't raise the rent to market level when a tenant voluntarily left and you rented to a new tenant, have been struck down.

Another Santa Monica situation: if someone purchases a multi-unit building (non-TORCA) and wishes to occupy a unit, they can evict only the most recent tenant of whatever size unit (measured by bedroom count) they want to occupy...they can't force out the tenant with the lowest rent, for instance.