Francesca Easdon said she wrote in the Nov. 12 note to her son, Kyler, "Please tell my son that his mommy loves him so much and that I'm thinking about him," KTRK reported.
When Easdon checked the lunchbox that night, she saw the note and a comment at the bottom: "No! Put him on a diet and go away!"
"I was absolutely livid and immediately reached out to the school," Easdon wrote in a Facebook post Nov. 13.
"It took a minute to register, what I even saw and I just kept rereading it and I just stood there for a minute," Easdon told the television station.
Easdon told KTRK she had recently made changes to her son's diet at Rocking Horse Day Care in Kingwood.
"I do everything in my power to build my son up and make him feel good about himself because he is amazing," Easdon told the television station.
The note upset Easdon. She alerted the owner of the day care center, who apologized and said the employee never intended for the note to be read.
"To know a grown-up who knows how hard life is and how mean people can be can say something like that, especially about a child is -- they're sick. There's something wrong," Easdon told KTRK.
A director at Rocking Horse Day Care said the employee was fired, the television station reported.
Easdon took her son out of the day care center and has brought him to her workplace while she tries to find a replacement,
"I'm worried about the higher cost but I will make it work, no matter what I have to do," Eason wrote on Facebook.