I believe that you're right on -- that she is hanging on to it, because she's getting a benefit out of it.
As morbid as that sounds -- it's morbidly true, with humans.
They will hang on to something that harms them --
in exchange for it fulfilling a perceived psychological need.
What's most unfortunate about it is: Most often, they are not aware that they are doing it.
It can be further understood in light of Dr. Silkworth's description of insanity:
"the inability to differentiate the true from the false."
It usually requires a "shock" to penetrate the shield of the mind. Saying something ludicrous and sometimes profane -- that they would never expect to hear from you.
1. "When is the last time you had good sex?" (They Answer) Then: "Do you believe that it's because God is holding out on you? That God isn't giving you the sex you deserve and could get if God wasn't keeping it from you?"
2. "How's your financial situation, are you broke?" (They Answer) Then: "Are you angry at God, because God hasn't given you the winning lotto ticket?"
3. "When is the last time that one of your sick kids got angry at you -- because you didn't keep them from getting sick?" Do you blame God for when you get sick?
It's advantageous to hang on to childish and sick ideas -- when we believe they are fulfilling a need, which we do not believe that we have a healthier option to fulfill it. It becomes "an easier softer way" to cope.
What's harming her is: "Her" concept of God.
What if -- she decided to "change" her concept of God?
Would the problem of anger go away?
The abuse was wrong. She has a right to feel angry because of it. However, the past can not be changed. The only thing that can be changed about the past -- is our present perception and understanding of the past. And, we do have to come to understand the past "from a different angle" before we can ever truly let go of it.
"IF" she couldn't blame God, for her present misery (which is anger) -- and the way she is punishing herself with it -- then, she would have to become 100% accountable and responsible for her present day misery.
It's a form of mental masturbation. Someone is getting screwed -- but, the fact is: they are screwing themselves. And, who wants to admit that they are screwing themselves?