Shakespeare introduces Hermia to us as the disobedient daughter of Egeus. She's supposed to marry Demetrius, but she's fallen in love with Lysander. Hermia could be mistaken for being young and foolish in love, but actually the whole thing is put in perspective by the fact that her father wants her killed (a standard punishment under Athenian law for disobeying one's father, apparently). She's been brought before Duke Theseus because of her father's complaint, and under these circumstances, she's pretty bold to stand up for herself.
Hermia doesn't want to marry Demetrius because she's true to her love. Her boldness is a little reminiscent of that favorite Shakespeare heroine, Rosalind in As You Like It. Like Rosalind, Hermia is no fool, and though she realizes that men break promises, she's willing to take a chance and run off with Lysander anyway.
Throughout the play, Hermia has to deal with her love being thwarted in one way or another. First, her father doesn't want her to marry Lysander. Then Lysander seems to no longer love her. Thinking this is Helena's doing, Hermia's willing to fight Helena (no matter the cost to their friendship) because, in her book, love is worth fighting for. Though all the other characters are willing to fall in and out of love quickly, Hermia knows love sometimes seems doomed, even if it's not actually doomed. Consequently, Hermia holds onto her love no matter the circumstances or consequences. Even after Lysander has deserted her, Hermia's final thoughts before going to sleep in the forest are of Lysander; she prays for his safety rather than cursing him.
For all these reasons, Hermia approaches love as though it were something easily threatened, but not easily lost. At all points, Hermia's relentless—you have to hustle if you're going to hold on to your lover, and it's worth the hustle if that love is true. Hermia thus provides a contrast to the self-doubting and flippant love around her. She may seem fierce and shrewd, but sometimes that's just the way love goes, unless you're willing to let it go all together.