Patty became a new leader of the community of those who survived the chaos by hiding in the Garden area after Dubois went missing in the ruins area. Patty helped the Initiate to recover after her battle with Attis and asked her to help her to shut down an auxiliary vent, so the people in the vault could escape through it to the wastes. While her plan succeeded, she didn't leave the Vault with the others.
She remained to make sure the Vault-Tec research would not become a plague to humanity and plans to use a nuclear warhead specially designed in case of an emergency. The emergency situation begins when Attis uses modified FEV strain on himself and transforms into a giant, regenerative blob that grows with each second.
She tried to make it to the warhead terminal, but was caught by Attis' tentacles. He began to grow inside her, slowly eating the woman. The Initiate found her, and she asked her to use the terminal, so the Vault and Attis would be destroyed. Before she goes, however, she asked him one more thing - to kill her, so she could avoid this terrible death.
The Initiate shot her in the next moment, saving her from suffering.
She is also a playable character after you complete Chapter One. She is very similar to Nadia, though she does have some extra advantages.