When Jimmy started talking about angels, Amelia thought that Jimmy needed help and even offered him medicines. She once returned home from running errands to find Jimmy's hand immersed in boiling water, unharmed.
She gave Jimmy an ultimatum: either he accepted to receive psychiatric help or she would take off to her mother's house with their daughter, Claire. When Jimmy walked away from her so as not to hurt her and accepted to be Castiel's vessel, she searched for him during his one-year absence but finally resigned and thought him dead.
When he came back, she was reluctant to allow him to meet their daughter. However, after Jimmy's claims were proven true by a demon attack, she apologized to Jimmy and escaped to safety with him and the Winchesters.
Jimmy had the brothers arrange a car for her to go back home. As the Winchesters, along with Jimmy, hit the road, they were called back and it was revealed that Amelia had been possessed by a demon and was holding Claire captive.
The demon possessing Amelia was able to capture Jimmy and the Winchesters and fatally shot Jimmy before ordering Claire's death. However, Castiel came to the rescue by possessing Claire and smiting two demons. Sam drank the blood of the last one and used his psychic powers to exorcise the demon from Amelia. Amelia watched as Jimmy accepted Castiel back into himself to save Claire and as Castiel walked off in her husband's body once more.
In The Things We Left Behind, Castiel tracks Claire to a group home where she tells him that after losing Jimmy again, Amelia dropped Claire off with her grandmother and then went off to "find herself." She still hasn't returned.
In Angel Heart it is revealed that after Jimmy became Castiel's vessel for a second time, Amelia began a search for him for years, sending her daughter postcards at her grandmother's where Amelia had left her. Her search eventually led her to Tulsa, Oklahoma in 2013 where she met Ronnie Cartwright who directed her to a faith healer named Peter Holloway who had healed his blindness. However, Holloway was really a Grigori named Tamiel who was feeding off of human souls and he imprisoned her and began feeding on her. Having lost contact with her mother, Claire believed that Amelia had abandoned her. After her disappearance, the motel manager found her stuff which eventually found its way to Claire at a foster home.
In 2015, Claire began a search for her mother using her diary and postcards. Claire's search led her to Tulsa where Amelia's diary had mentioned her meeting with Ronnie and her last postcard said she had been. After learning of what was happening, Sam, Dean and Castiel aided Claire in her search and with information from Ronnie and hacking Amelia's credit card records, they finally located her. While Castiel was able to wake her up, he was unable to heal the damage that Tamiel did to her. Amelia was grateful for Castiel's rescue of her even though she could tell Jimmy was no longer there and was happy to hear that Claire was alright, saying that as long as Claire was fine, Castiel kept his promise to Jimmy. After finding out that Tamiel was a Grigori, Dean and Claire came to rescue Sam and Castiel and mother and daughter had a tearful reunion. As Claire tried to help a weak Amelia out of the barn, Tamiel appeared and told them that Amelia was beyond saving. Claire tried to kill him with a gun and failed so Tamiel tried to kill her with his angel sword, but Amelia sacrificed herself to save her daughter. Her death was avenged minutes later when Claire killed Tamiel with his own sword.
After her death, Amelia went to Heaven where she was finally reunited with the real Jimmy. Amelia told Jimmy about their daughter and how proud she was of her and the two embraced.