"Does anyone else remember that one time in 2020 when your sister, who was your best friend for your entire life, decided to get engaged to your ex-husband?" she said in the clip posted to TikTok.
In a series of videos, she referred to her relative as "trash" and described the situation as a "dumpster fire".
She also said that when she was married to the man, who is 20 years older than her, he did not get along with his then-sister-in-law.
The TikTok user said she found it "weird" that, following her divorce, she did not hear from her sister for a long time.