consider this: “Terezi’s” is grammatically incrorect; Terezī is already in the genitive, and her name is actually Terezus
Singular
Nominative: Terezus
Genitive: Terezi
Dative: Terezo
Ablative: Terezo
Accusative: Terezum
Vocative: TerezePlural
Nominative: Terezi
Vocative: Terezi
Accusative: Terezos
Genitive: Terezorum
Dative: Terezis
Ablative: Terezis