The ruling on a mother saying to her son in anger: You are a disbeliever

Question:
Honorable Shaykh, may Allah grant you success, a woman strives to keep her children up to date with performing the five daily prayers in congregation. One of them repeatedly delays going to the mosque until the imam has prayed more than one unit of prayer. One day his mother became angry with him and said to him, "You are a disbeliever." The word came out of her without thinking, and afterwards she regretted it intensely, thinking about the consequences of this word day and night. She wants to know from your eminence what she must do now, hoping that Allah will forgive her?

Answer:
If she said this in intense anger, there is no blame on her, because when one is angry, one says something one cannot hold back. If this was due to anger, there is no sin in it. Yes.