Dallas County investigators say Kariasa Thomas took the four children, aged 3-7, to the swimming pool in her apartment complex, and was joined by her 16-year-old daughter and legally blind husband.
Though the pool was closed for the day, Thomas decided to enter anyway after noticing some people in the water.
Thomas told investigators she knew 3-year-old Kanyce Giddings couldn't swim, but allowed her to stand on the pool's steps with her feet in the water.
After 15 minutes, the building's security guard arrived and asked everyone to leave the pool.
While collecting the children, Thomas saw that Kanyce was missing, and, after entering the water, soon found the toddler's lifeless body inside the pool.
An attempt by the guard, an off-duty Dallas police officer, to revive the child failed, and she was later pronounced dead at Methodist Charlton Medical Center.
She was booked into Dallas County jail where she remains on a $25,000 bond.