Littlehorn, who joined other family friends at a police command post, said authorities separated the two parents for hours Saturday as they questioned them. She said it was difficult for them knowing their little girl was out there somewhere.
"She hasn't been allowed to help look for her daughter," Littlehorn said of Becky Celis.
Littlehorn has worked with Becky Celis as a registered nurse at Tucson Medical Center for five years. She said Isabel, whose nickname is Isa, loved to play baseball and dance; the girl was supposed to play in a baseball game Saturday.
"She's just the sweetest, she is feisty, she's full of life and spirit," Littlehorn said.
She said Becky Celis is a registered nurse in the pediatrics unit and Sergio Celis is a dental hygienist. There's no way anyone in the family is involved in the disappearance, she said.
"We all feel this is somebody who's been watching `Isa' for some amount of time to know where her bedroom is," Littlehorn said.