Explanation:

- Poverty was staring her to the face: This phrase is incorrect. "To the face" is not a standard English expression for confronting something directly.

- Poverty was staring her in the face: This phrase is correct. "In the face" indicates directly confronting or encountering something unavoidable or obvious.

- Poverty was staring her at the face: This is incorrect. "At the face" doesn't convey the same immediacy or directness as "in the face."

- Poverty was staring her on the face: This is incorrect. "On the face" is not appropriate for this context.