Dianna Agron Says Lindsay Lohan's Life Is "Sad"

Glee's Dianna Agron is Cosmo's latest cover girl, but she doesn't open up about her personal life much ... and Lindsay Lohan is the reason why!

Says Dianna:

"It's really sad looking at people like Lindsay Lohan. She's an amazing actress, but you see what happens when people know too much about your personal life. [People] start not being able to look at you the same way professionally. I don't want that to happen to me."

Smart! After all, Lindsay's been doing more hanging out than making movies lately.

Dianna is looking sexy and acting smart - winning combination!