She's feeling envious.
She is popular, she has money, she had a boobjob, yet, she won't get any solos, she doesn't get a boyfriend, while Rachel the dwarf and Brittany do have both, and seemed very happy about them and she's not longer the Head Cheerleader. Brittany and Quinn are quite well adapted to the glee club. They are popular and the whole group like them. Puck might still having sex with her, but he now wants to improve himself. Everyone is moving on but her.
I wouldn't blame her for trying to get Finn, who turned out to be a good boyfriend.
I agree. But there is something in the back of my head, thinking that she is jealous of Rachel. I think she may have some feelings for Finn. I for one, would love some Finntana. Just saying