Hero describes her cousin Beatrice as a very selfish person who judges men harshly. Hero describes Beatrice in this manner in order to persuade her to amend her ways and fall in love with Benedick.
In the first speech Hero uses to describe Beatrice, Hero calls her a proud woman who dislikes and ridicules everyone, as we see in her lines:
But Nature never framed a woman's heart
Of prouder stuff than that of Beatrice.
Disdain and scorn ride sparkling in her eyes. (III.i.50-52)
Hero also claims that Beatrice values her own wittiness, or ability to be clever and amusing, so much that everything else seems trivial, as we see in the lines:
[A]nd her wit
Values itself so highly, that to her
All matter else seems weak. (53-55)
In this passage, we also see Hero make the claim that Beatrice is so selfish that she is incapable of loving another person (55-57).
Hero also makes the claim that Beatrice is so very critical of men that she finds fault with all of them and never even tries to see their merits, as we see in her lines:
She turns every man the wrong side out
And never gives truth and virtue that
Which simpleness and merit purchaseth. (70-72)
Finally, Hero argues that she is going to try and convince Benedick to forget about his love for Beatrice, for if Beatrice knew about it, she would "mock" him to death. She also says that it would be better for Benedick to die of unrequited love for Beatrice than for her to mock him to death, as we see in the lines, "It were a better death than die with mocks, / Which is as bad as die with tickling" (81-82O).
Hence, we see that as part of the trap Hero is laying out for Beatrice, Hero is purposely calling her beloved cousin many horrible things. Hero calls Beatrice selfish, prideful, and overly critical.