Before a person takes a bold step in life, they must make a declaration of their intention (to themselves or to another key person in their life). Your mom has made such a declaration, so that's a great first step.
Now you'll see if she stays focused and single-minded in that determination. As noted before, she's gone back and forth a few times. If she had acknowledged that in her letter I'd feel closer to 100% that she'll really mean it this time. Maybe she does though!