"We are very amazed by the response from this," Emily Enderle told ABC. "It has been such an amazing output of love and generosity."
The Mid-Michigan girl has been battling cancer most of her young life. At 13 months, she was diagnosed with stage 4 neuroblastoma, according to her YouCaring page. Last June she had a kidney transplant, after which she spent two months in the hospital, her mother told ABC.
"The mail I think helped make her feel loved," Emily said of Olivia's time in the hospital.
So when her birthday rolled around, she knew what to ask for to make Olivia's day special.
About two weeks before the big day, her family posted on her Facebook page that Olivia wanted to try to get 100 cards for her birthday.
The community caught on, and soon Olivia was receiving hundreds of cards. The family received more than 2,000 cards, many of them handmade. Some even came from firefighters and police officers around the country.
"Her favorite card so far is a fuzzy one that makes silly noises and a couple cat ones that meow happy birthday," her mom said.
Some well-wishers even included Olivia's brother so he wouldn't feel left out, Emily said.
The post office went out of their way to deliver all the extra mail, Emily said. Local firefighters also got involved in making her day special, giving her a ride in the truck.
As for the birthday girl, her mom said is doing well and continues to get cards in the mail.
"We would love to say thank you to everyone for reaching out and bringing some happiness and excitement to Olivia," she said. "It has been her best birthday yet."