Scarlett Middleton died of sepsis just days after celebrating her 5th birthday at Walt Disney World with her mother and grandmother

Girl, 5, Dies Suddenly After Trip to Disney: 'I Thank God I Was There When She Passed,' Mom Says

Just days before her death, 5-year-old Scarlett Middleton was parading around Disney Springs dressed as The Little Mermaid. Now, her family is struggling to grapple with what followed the birthday trip to the most magical place on earth.

Holly Middleton, of St. Petersburg, Florida, says her daughter began vomiting and came down with a fever on July 9, just one day after they returned home from their Orlando visit. Scarlett frequently battled colds, and even suffered mild febrile seizures — which she took medication for — so Holly says she expected her daughter’s latest symptoms to pass.

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“She threw up and we noticed she had a fever,” Holly says of that night. “The second day she had a fever, so I called our doctor and I took her in. She was so lethargic I had to carry her into his office. [The doctor] thought it was a stomach virus, so he gave us zofran and we took her home.”

Image zoom Holly (left) and Scarlett Middleton

On July 12, Scarlett began to improve, Holly says. Her fever went down and the little girl acted “normal.” The mom of four was pleased, but couldn’t help but notice that her daughter had become bloated.

“I put Scarlett down for a nap and was laying next to her when I noticed she started burping. Her stomach got really big and she was burping a lot,” she recalls to PEOPLE. “I called her doctor … I said please call me back. When I hung up the phone, I saw her eyes roll back.”

Holly quickly called an ambulance and carried Scarlett out to the vehicle when medics arrived. She climbed into the ambulance with her ailing daughter and paramedics assumed Scarlett was having a seizure. Then, the situation took a turn for the worst.

“Her heart stopped in the ambulance and they couldn’t restart it,” Holly says, noting that doctors worked to save her when they arrived at the hospital. “I thank God that I was there when she passed. I was talking to her when they were trying to resuscitate her. Her last words were, ‘I want my mommy.’ ”

Image zoom Trott (left) and Holly Middleton Hannah Sanchez Photography

Holly’s husband, Aaron Middleton, a 37-year-old Marine, returned home immediately. Just one day after Scarlett’s death, the family learned that she died of sepsis — but officials have not been able to determine how she got the illness.

“We really want to know how she got sepsis. How did this happen? Is this possibly genetic? We have three other children, we don’t want to lose our other babies,” Holly says through tears.

In the wake of the death, Holly’s friends have rallied behind her, supporting her and helping around the family’s home.

“The first month was terrible, the first week was terrible. I woke up the day after [her death] just vomiting. It was really dark and really bad. I turned to alcohol to ease the pain,” Holly tells PEOPLE, noting that she has been sober for two weeks. “I have traumatic visions of her dying. I just try to get through each day.”

The death has been hard on Holly’s 7-year-old son Trott Middleton, who she says was very close with his little sister.

“He lost his best friend. He was a great big brother to her,” she says of Trott. “He’s cried a lot. He talks about her often. I know he misses her a lot. There’s a tree planted at the school they went to. He went there last week and told all his friends, ‘This is my sister’s tree.’ And they all comforted him.”

Image zoom Holly Middleton and her children

Holly and Aaron are also parents to Magnolia, 3, and 10-month-old Kelvin. A GoFundMe page has been set up for the family.

Amid her grief, Holly, who first shared her story with Love What Matters, launched Scarlett’s Sunshine, to inspire random acts of kindness. Holly often travels around her community, handing out flowers to people to spread Scarlett’s “sunshine.”