Are you trying to say she stays busy?

It sounds fine to me if you're trying to say she keeps herself busy 24/7 Maybe rephrase: She has a habit of constantly working on something.

Ok

In my opinion, "She has a habit of regularly working on something" sounds better. However, I don't know the complete meaning of the sentence, so it's hard to give an objective answer.

It would make more sense if 'something' was more specific.