Oliver's younger sister, Grace, was diagnosed with an aggressive brain tumor, and she died last summer. Prior to Grace's passing, Molly learned that she had breast cancer, but she kept her diagnosis private until two weeks after the funeral.
According to a Molly's friend, Megan Crawford, Molly's own battle was less important to her than people fully honoring Grace's memory. On Sunday, Molly joked that Grace was not only responsible for the beautiful weather at Wrigley Field but also playing tricks on her. Molly had attended a cousin's wedding Saturday, and she left her makeup at the hotel.
"She messed with me today," Molly said, smiling. "It's like, 'Thanks, Grace.' She's with us."
Oliver's mother also was at the game, decked out in pink to join the Mother's Day celebration.
"She's really excited," Molly said. "It's an honor for her to be here with me today."
Molly was diagnosed with Stage 2 breast cancer, and said that she's finished her chemo and radiation. Her hair is growing back and she'll be completely done with treatments by the end of July.
She provides updates to her inner circle of friends and family that feature "Cocktail Friday," referring to her chemotherapy, and "Feelin' the Burn," in reference to her radiation. And she signs every email with her mantra, "Full of Grace."
Crawford submitted Molly for the MLB Bat Girl campaign, and wrote: "Molly is a diehard Cubs fan. In her email revealing her diagnosis, she wrote: 'I know what you're all thinking, What do I need? I don't really need much other than this to be over. I will be happy to reach out to you all if I do need something, like maybe the universe to cut me some slack for a hot second and let the Cubs win the World Series."
She'll have to wait until October to see if that happens.
Authentic game-used Louisville Slugger pink bats and other gear from Mother's Day games will be auctioned exclusively at MLB.com, with proceeds benefiting the fight against breast cancer. The complete Mother's Day collection -- which includes the special caps and jerseys being worn by players on Sunday -- is available at the MLB.com Shop.