Am I obligated to help my mother disobey her father, or should I leave her angry with me, especially since she is very problematic and caused my brother and me to leave the country?

There is no obedience to a creature in disobedience to the Creator. Therefore, obeying the mother in her defiance of the father, or her desire to live with you, which causes discord, is not permissible Islamically. The obligation is to provide for her if the father refrains, because defiance (nushuz) abrogates the wife's right to maintenance, but it does not abrogate the mother's right to maintenance from her children. The mother's anger in this case does not necessitate the Lord's anger. You are not obligated to assist her in her defiance, and we do not advise taking her to live with you due to the harm that might result, and "there shall be no harm nor reciprocating harm."