Does my saying "I hate you and I hate your destiny" in a moment of extreme anger constitute disbelief (kufr)?

Mere displeasure in the heart may lead a person to disbelief if its cause is doubt in God's wisdom or objection to His Lordship. What then, if one expresses this with their tongue? The Prophet, peace and blessings be upon him, said: "Indeed, Allah does not punish for the tears of the eye nor for the grief of the heart, but He punishes with this — and he pointed to his tongue — or He shows mercy."

There is no doubt that the mentioned heinous statement is clear disbelief. Nevertheless, God accepts the repentance of whoever repents, no matter how great their sin. Allah the Almighty says: "Will they not then turn to Allah and ask His forgiveness? And Allah is Forgiving and Merciful." (Al-Ma'idah: 74), and His saying, exalted be He: "And if only the People of the Scripture had believed and feared Allah, We would have removed from them their misdeeds and admitted them to Gardens of Pleasure." (Al-Ma'idah: 65).

Therefore, the questioner should utter the two testimonies of faith and hasten to sincere repentance, regretting what she said and resolving not to return to it. Allah the Almighty says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" (Az-Zumar: 53).