I agree about the maturity factor.

I also agree with the talk above about self-esteem.

I know of agreat many exercises and worksheets that pertain to this but it would be ludicrous for you to be the one to give them to her. She needs to take the bull by the horns and get help for this herself.

As such, there are ways of being supportive and encouraging without telling her how to feel better. You can subtly get her to talk by asking questions like, "You seem better today, tell me how you are feeling" "What did you think of such-in-such?" "I noticed xyz got you a bit down, how could it have been better." Essentially you want to ask questions that demand multi-word answers instead of those that are close ended (questions that require only one word to reply).