DiannAgronCosmoCover230.jpgGlee'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!