I am livid!!

Very livid!

My sister is having sexual intercourse with my ex and my mother is in support of it just because my sister gives her some of the gifts and money that my ex gives to my sister. My mum seems to think that there’s nothing wrong with that because “after all he is your ex and you are no longer together”. I feel betrayed by my sister for sleeping with someone she KNOWS that I dated and slept with countless of times eww and she has the cheek to be proud of it