I don't think that Mrs. Mallard fights her feeling of freedom, in fact, I think she has to contain her joy at the thought of this freedom. It is the idea of freedom, the absolute exhilaration from it that she must keep in check, she is expected to be mourning the sudden death of her husband. It would be inappropriate for her to appear happy at this sad time so she must conceal her joy at the thought of being free.
That is the struggle that Mrs. Mallard has emotionally, not the idea that she doesn't deserve to be free. She has desired to be free for so long that when she gets what she wants most in life, she can't believe that she could be so fortunate. It is like getting the one thing that you want most in the whole world, when you get it you just can't believe it.
It is so overwhelming that at first you feel giddy with a dreamlike feeling, that is the way the Louise Mallard feels when she gets the news of her husband's death. Light-headed with utter relief at her good fortune to be given her heart's desire.
It is the thought of losing this wonder gift of freedom at the end of the story, when her husband walks into the door, fine and fit, that she dies, overcome from the pain of having to surrender her life to the control and domination of another.
Mrs. Mallard had the freedom for only a short period of time, and it was only in her mind that she was able to enjoy it, but for that little amount of time, she was happier than she had ever been in her life.