“A compassionate but flawed heroine.” Discuss Shakespeare's presentation of Cordelia in light of this statement.

Cordelia is undoubtedly the only one of Lear's daughters who has any genuine love or compassion for her father. But because she isn't prepared to play along with the charade of insincere public flattery, she falls out of favor with him. It's only much later in the play that Lear finally recognizes that Cordelia was the only one of his daughters who truly loved him. But by then, it's too late for both father and daughter.
It could reasonably be argued that Cordelia's tragic flaw is her total honesty. Instead of indulging in the same kind of shameless flattery as her sisters, she believes that the best way of showing love for her father is through actions, not words. And right throughout the play she displays that love, as well as her goodness and integrity, for all to see:

O dear father, It is thy business that I go about; Therefore great France My mourning and importuned tears hath pitied. No blown ambition doth our arms incite, But love dear love, and our aged father’s right. Soon may I hear and see him (Act IV, Scene iv).

But in such a thoroughly dishonest, cutthroat world, virtues like these are of no avail. Cordelia is simply too good, too pure, too noble for such a brutal, unforgiving world. She represents the last chance of redemption for Lear, the last flickering beacon of hope. Once she dies, all hope is gone, and Lear's own death is inevitable.