Is it permissible to refuse gifts offered to children by their aunt who insults the parents, and is it permissible to deprive the children of visiting her?

The sister has combined several forbidden acts: imitating Christians, not adhering to Islamic obligations such as hijab and prayer, and being disobedient to her parents by insulting and cursing them. She must hasten to repent. As for how to deal with her, it depends on what brings benefit and what causes harm. If maintaining ties with her leads to her guidance, then that is better. If shunning her leads to her abandoning sins, then that is better, while being careful not to be influenced by her behavior.