Quote 1
HELENA
How happy some o'er other some can be!
Through Athens I am thought as fair as she.
But what of that? Demetrius thinks not so.
He will not know what all but he do know.
And as he errs, doting on Hermia's eyes,
So I, admiring of his qualities.
Things base and vile, holding no quantity,
Love can transpose to form and dignity.
Love looks not with the eyes, but with the mind;
And therefore is winged Cupid painted blind.
Nor hath Love's mind of any judgment taste.
Wings and no eyes figure unheedy haste. (1.1.232-243)
When Helena admits that she loves many of Demetrius's "base and vile" qualities, she recognizes that her love has made her "blind" in that her judgment has been skewed by her passion. This idea resurfaces throughout the play, especially when Titania literally falls in love with a "base and vile" creature—an "ass."
We also want to point out that Helena is acting a little immature here when she complains that most people think she's prettier than Hermia. Apparently, love also makes us self-absorbed.
Quote 2
HELENA
He will not know what all but he do know.
And as he errs, doting on Hermia's eyes,
So I, admiring of his qualities.
Things base and vile, holding no quantity,
Love can transpose to form and dignity.
Love looks not with the eyes, but with the mind;
And therefore is winged Cupid painted blind. (1.1.235-241)
Here, Helena admits that she loves many of Demetrius's "base and vile" qualities. It seems that love has the capacity to blind us (figuratively speaking) to the truth. This idea comes up again when Titania literally falls in love with Bottom—a "base and vile" creature.
Quote 3
HELENA
Ay, in the temple, in the town, the field,
You do me mischief. Fie, Demetrius!
Your wrongs do set a scandal on my sex.
We cannot fight for love, as men may do.
We should be wooed and were not made to woo. (2.1.245-249)
Here, Helena points out that, even though it's not socially acceptable for women to be aggressive in the pursuit of love, she doesn't care. On the one hand, Helena acts like a creepy stalker when she chases Demetrius around after the guy's made it perfectly clear that he's not in love with her. On the other hand, Helena's point about double standards raises an interesting question: Why is it OK for men to "fight for love" when women are expected to be passive? Remember, Theseus literally won Hippolyta with his "sword" when he conquered her people (see quote #2).