Helena,suffers from insecurity due to Demetrius's rejection of her. More than just rejecting her, they were actually engaged before he started pursuing Hermia. As a result of her insecurity, like most women who become insecure due to love tribulations, one of her personality traits is being diffident, meaning "lacking confidence in one's own ability [or] worth" (Random House Dictionary). We first see evidence of her diffidence when Hermia greets her with the exclamation "fair Helena" and her only reply is to mope about how Demetrius thinks Hermia is fair and not Helena. We further see evidence of her diffidence when she decides to throw her friendship with Hermia to the wind and tell Demetrius of Hermia and Lysander's plan to elope and run off into the woods with nothing more than the hope of receiving a thank you from Demetrius for the news. Since this act of betraying Hermia really will gain her nothing, it shows us her underlying feelings of lack of self-worth.