Ignore is the best solution; I was in similar situation like you before but for me is my sister. She will block me when other family members praise my children instead of her or get presents for my kids' birthday (her kids also received presents on their birthday from same relatives). In the beginning, I did the same by explaining or apologies for the sake of harmony in our family, which is a wrong move. People with this kind of mentality will only keep pushing their luck when you give in. Long story short, she blocked me again and being nasty to my children again after someone bought my girl a toy instead of her kid, so I DID the same and never feel more happy than before. Life is so stressful already so don't give those energy sucker any chance to drain you further.
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