DD went to school with a girl like this in primary.
When we joined the school we were warned to keep DD away from her because she was a bit of a "performer" and didn't quite grasp what was and what wasn't appropriate.
We didn't listen, and the child monopolised every situation that she could. If there was an assembly, whether it was whole school or year it would turn into (girls name) show.
Children didn't much like being around her, and parents would find it annoying because we knew that she would manipulate every school event to be about her. Think of singing at the end of every assembly, or a dance performance, or a story about her family, or a poem that she had written.
They went out as a group when they finished primary, this child again monopolised the entire outing. When the girls tried to move on the situation from her, she tried to say she had lost her money, and had the girls searching the town for the money she had "lost" she told them that they could all pay her some of the money she lost.....then found it in her purse.
When they went up to Upper school the children that she did know from primary wanted nothing to do with her, and she hasn't managed to find new friends. She has stopped with the attention seeking. She's spoken to DD a few times in the past few years, she's very unhappy. They attend different schools, but we've driven past her quite often, she's always alone.
Your DNs parents are not helping her at all.