Hi, Try ignoring it. She is probably doing this for the reaction you are giving. I would totally ignore her when she tells you. i would clean it up when her attention is elsewhere. If this doesn't work after a good effort i would take her to the doctors.
Well...if she was a puppy I'd supervise her and not let her be alone in the room in question and redirect her BEFORE she initiates the behavior. Use a child gate to keep her from entering the living room.
You don't fill in many details, so it's hard to tell why this child is with Grandma instead of her parents, which might be causing this attention seeking behavior.
Since it's not clear whether she does this on regular "Grandma" visits, or if in fact you are the full custodian of her at this point, it's hard to tell.
Can you provide more details?