Without more context, it is difficult to determine why the old woman was angry at the sky. However, it is possible that she was upset about the weather or some other natural phenomenon that was beyond her control.
For example, if there was a severe storm or heavy rain, the old woman may have been angry at the sky for causing the bad weather that was impacting her life. Alternatively, she may have been upset about a lack of rain or sunshine, which could have affected her crops or other aspects of her life.
It is also possible that the old woman was using the sky as a metaphor for something else that was making her angry, such as a political situation or personal issue. In this case, the sky may have represented the larger forces that she felt were causing her problems.
Without additional information, it is impossible to say for certain why the old woman was angry at the sky. However, it is clear that her emotions were likely tied to some external factor that was beyond her control.