Black Child Isolating with Grandmother After Being Traumatized at Sesame Place

One of the Black girls who allegedly got snubbed by a character at Sesame Place is still reeling from the incident ... and is now isolating with a family member to regain stability.

B'Ivory LaMarr -- the attorney for the family whose kids interacted with Rosita at Sesame Place -- tells TMZ ... the girl in question has been traumatized by the incident, and is staying with her grandmother so she can be shielded from the publicity in a safe environment.

LaMarr tells us the little girl has been overcome with emotion, crying and upset because she can't understand why Rosita would treat her differently than white kids.

One of the things we're told ... she asked her mother in the immediate aftermath whether she'd done anything wrong ... seeing how the Sesame mascot refused to touch her or the other Black girl, but had interacted with white girls just moments earlier.

LaMarr says he and the family are working on setting her up with therapy sessions.

As for what's on the horizon ... we're told a Change.org petition has been set up to ID the person in the Rosita costume ... with the goal of accountability. LaMarr previously told us they're also mulling over a lawsuit.

As we reported ... similar videos have now surfaced -- Sesame Workshop has apologized and promised more bias training.