Well, all the articles describe her as developmentally disabled and it doesn't take an intuitive genius to see from her pictures that she's obviously not a healthy person/probably doesn't have a super high IQ.
Developmentally disabled doesn't always mean the person is also mentally disabled. Granted, she doesn't look like she has the total mental faculties of a regular 19 year old, but it also doesn't mean she has the intelligence of a 6 year old.