forcible entry

Our property was taken unlawfully from us more than 10 years ago. Because of the threat in my mother's life and for lack of resources as well, we only made actions to recover our property only a year ago. The people who unlawfully took possession of our property leased it to several lessees. When my mom came back to the property and talked to the lessees, they turned over the property back to my mom extrajudicially, comes now the lessor who unlawfully possessed our property, she filed a case of forcible entry against my mom. does she have the right to file such action, since she is not the lawful owner and has waived her right of possession since she leased the property which is not even hers? please shed us light on this. thanks

sana po makabigay kayo ng advice.. intayin ko po