The Rush Hour 2 star visited the San Jorge Hospital in San Juan in a bid to boost patients' spirits as part of her role as a sponsor of the San Jorge Foundation.
However, Sanchez - who is mum to eight-month-old daughter Sebella - was so touched by one young girl's positive attitude, she had to leave the room to weep.
She tells Fox News Latino, "I can't explain the feeling to you. It was from the fibre of a mother's being. All these mothers had a healthy child, but suddenly they find something. In that girl, I saw my daughter and I asked God to take care of her for me."