What should my friend do when she sometimes invokes against someone, contrary to her will, instead of praying for their well-being, and some of these invocations come true, causing her distress and fatigue?

Supplicating against others unjustly is an act of wrongdoing and aggression. However, if it occurs unintentionally, there is no sin. For those who fear this, one must refrain from supplicating for or against others. It is advised to perform ruqyah (Islamic exorcism) as there might be a jinn possession causing this, and perhaps the supplication coincides with a time of acceptance. The Prophet, peace and blessings be upon him, said: "Do not supplicate against yourselves, and do not supplicate against your children, and do not supplicate against your wealth. Do not coincide with a time from Allah when a gift is requested and He responds to you."