When we talk about what separates us from God and from being the people we long to be, we tend to give a lot of time to guilt, both on the objective side (our performance failures.....we have some real things to feel guilty about) and the subjective side (feeling unworthy makes it hard for us to accept acceptance and forbearance, because we can't believe we deserve it). But the true obstacles between us (us and God, us and each other) often have different, more concrete profiles. Sometimes it is the deeply toxic blend of bitterness and disappointment. In Valjean's case, it is bitterness over his unjust treatment that breeds hatred and hardness toward others. For Éponine it is the simple bitterness of disappointed love. She loves Marius and Marius does not love her. Both sides of that coin are among the most awkward, and often destructive, of our social relations. Even at the middle school level, it is serious business. Hugo does not blunt the edge of this. Éponine has been dealt a cruel hand in life (look at her parents!) and nonetheless we see her beauty and her honesty and her longing for something better. In a just world, Marius would love her instead of the privileged Cosette, and take her away from all this. So she might feel, and we can feel it on her behalf. But life is rarely so simple, and the complicated truth is that as children Éponine was the one privileged by her parents at the same time they abused and disparaged Cosette.
Éponine triumphs in a way that may be even more unusual than Valjean's moral turnaround. Her limpid longing for Marius never curdles into hatred toward Cosette or him. She cherishes the lesser but real affection he can give her. In the crisis, when she could easily sacrifice the happiness of Marius and Cosette---if I cannot be happy, why should they be?---she does not. The musical has Éponine die in Marius' arms while they sing a duet----a four alarm formula for the sappy and the saccharine. If it avoids that fate (some may differ how far it does--give a listen below) it is because the reality it expresses is not a conventional one. This is not the tragedy of star-crossed only loves. It is the more rare, and spiritually more impressive reality--- the disappointed and the (no fault of his own) disappointer claiming what is good in a relation that is not what either of them would want it to be.