Lea Michele is reportedly upset she is being given fewer solos on 'Glee'.
The 24-year-old actress - who plays uptight singer Rachel Berry in the musical TV show - is angry the second series has focused less on her and more on other characters.
A source said: "In the beginning, she was the biggest star. But some of the biggest episodes have taken attention away from her, like the Britney Spears show, which was all about Heather Morris (Brittany).
"She thinks that because she has a Broadway background, this show was made for her."
Lea has allegedly been critical about some of the efforts of her co-stars - which include Amber Riley, Chris Colfer and Dianna Agron -leading to friction on set.
The source added to Britain's Star magazine: "It's not easy being around Lea on set. She has put several people's backs up and it's showing no sign of improving."
Lea has previously admitted working on 'Glee' helped boost her self-confidence about her looks.
She said: "'Glee' has made me feel beautiful. It has shown me that I am beautiful, that I can be beautiful no matter what I look like, what my weight is."