After the war ended, Mary was made a villain because people blamed her for everyone's deaths. Never mind the fact they were all capable adults and looked toward a teenager to save their asses. They had no spine to speak of. Mary hated weakness, and she hated the wizarding world from the moment she entered Hogwarts. Something deep-seated in her told her to be cautious, and she was happy she did. She knew she wasn't meant for this world, it felt forced upon her. She wasn't a born witch. She knew Dumbledore had something to do with whatever the hell happened to her.
Mary had always known Lily and James hadn't been her parents. She had an eidetic memory, so she knew Dumbledore had murdered her birth mother, and that her father had tried to rescue her along with her brother's that night, but before he could, Dumbledore had already disappeared with her. Mary knew that they thought she was dead until she had sent a letter just this year charmed, so they could view her memories.
Mary packed all of her belongings and made her way to the bank. She did a ritual after they performed an inheritance test, and had them remove the magic within her. When the ritual was done, Mary felt like a weight had been lifted from her shoulders. She sold everything she had, including her shares to every wizarding business except for the weapons she inherited. The only thing Mary kept was Sirius's motorcycle, which she had shipped to her home in California. She purchased a one-way ticket and never looked back.
When she arrived in Eureka, California, and headed straight to a dealership. She purchased a 1967 cherry red Camaro and made her way to her new home. It's a large home, but her favorite rooms were the gym, billiard room, home theater, pool, and a bunker with a training room and weapons.