Maria is a gentle soul. That's part of her charm. She seems innocent and naïve like another young maiden in similar circumstances, but she's also smarter than a lot of people. Smart enough to know that she doesn't love Chino, and that marrying him would be a big mistake.
MARIA: Chino… when I look at Chino, nothing happens.
ANITA: Well, what do you expect to happen.
MARIA: I don't know. Something.
She's also young, and when you're young, you think you're bulletproof. She's a recent immigrant to America and ready to explore her new world. That gives her an energy and an enthusiasm that not a lot of other characters possess. She's ready to get out there and go, and she really isn't afraid of the consequences, even though her brother and Anita try to rein her in.
And yet she's smart enough to spot some of those pitfalls.
She knows what she's getting herself into, especially with Tony, but she chooses to go forward anyway. Because her love is absolutely worth it to her. She even forgives Tony for killing her brother. Why? Because she's smart enough to know that the hate and anger in their neighborhood is what created the problem in the first place.
TONY We'll be all right, I know it. We're really together now.
MARIA: But it's not us. It's everything around us.
It's love that she cares about, and once her mind is set, nothing's gonna change it:
MARIA: I have a love, and that's all that I need,
Right or wrong, and he needs me too.
I love him, we're one, there's nothing to be done.
Not a thing I can do, but hold him, hold him forever;
Be with him now, tomorrow and all of my life.
MARIA AND ANITA: When love comes so strong,
There is no right or wrong;
Your love is your life.
Seriously, the guy killed her brother. And yet she's instantly ready to believe that it was all in self-defense. She takes Tammy Wynnette to a whole new level. Maria reaches that well-adjusted forgiveness on her terms, not Anita's or Tony's or anyone else's. When Anita spends a whole darn song trying to turn her against Tony, she just doesn't buy it:
MARIA: It isn't true, not for me,
It's true for you, not for me,
I hear your words--
And in my head
I know they're smart
But my heart, Anita,
But my heart
Knows they're wrong.
What can we say? The girl's got heart.
That gives Maria the strength to overcome the biggest obstacle of all: Tony's death. She tells the other kids that she now can hate like them, but she doesn't kill them or herself. She doesn't pull the trigger on that gun. Like Tony, she's stronger than anyone else in the story, which means she gets to suffer for the world's sins, too.
She takes a last stand:
MARIA: You all killed him. And my brother. And Riff. Not with bullets and guns. With hate!
So yeah, things don't go well for the innocents in this movie, and Maria's the most innocent of all. But while it may hurt her more than anyone, she can bear it.