Here is what I would do

1) go to the apartment and tell the wife that she is not on the lease. You are the landlord and demand her to leave the property.

2) If she refuses to follow your order, call police at the spot and declare her invading your property (illegally occupy your apartment). Police should be able to remove her from your property.

3) She is not a tenant, and she should not have the right to stay since she is not on the lease. The two brothers abandoned the apartment since they are not living there for a long time. This is your legal base if she argues with police.