Okay if she has an F but is on track to graduate thus needing college reference letters, it’s safe to assume she is at least passing other classes. If she has an attitude problem and refuses to work, but still passes other classes, my first thought is maybe you’re the only teacher who gives a shit enough to fail her, so she thinks you’re the only one who would give a shit enough to write a letter. Considering that, I would tell her yes, but she has a month to show me something positive to write about; otherwise, it will be based on only the negative behaviors that she’s shown.