Shell, what a very special story you shared.
My grand-aunt was a die-hard Cubs fan. Growing up in the 70s I counted on a package from Chicago every birthday and xmas. While she didn't have a lot of money, she'd manage to send me a Cubs sticker and something biblical every holiday. She too suffered from dementia, and it tore my heart out. She went into assisted living in her mid 80s and died 2 years ago at 98.
Your mom, like my Aunt, is the best kind of fan. Undying loyalty and a passion for every player and every season, regardless of win-loss record. In the days where the majority of fans are either fantasy statistic obsessed or those who use social media to bitch about their teams, there will always be the fan like your mother. The Angels may not be clear in her mind, but they are enormous in her heart.
The fact that she brought you up in that environment is awesome. Hopefully you can decorate her room with some Angels mementos so that every once a while, the spark in her mind will fire up for the Angels.