Is the questioner considered sinful for cutting ties with her relatives who do not wish to communicate with her and change their phone numbers to avoid her?

Maintaining kinship ties is obligatory, and severing them is forbidden. Your relatives' act of severing ties does not negate their right to be reconnected. Rather, it is obligatory to maintain ties with them to the extent that reconnection is achieved. And Allah does not let the reward of those who do good deeds go to waste. Allah Almighty says: "Nor can goodness and evil be equal. Repel (evil) with what is better: then verily he, between whom and you was hatred, (will become) as though he were a close friend." And in the Hadith: "Connect with him who cuts you off, and do good to him who wrongs you."