<human>: Can you give me the gist of the text in a nutshell?

To begin, my relationship with my SO has been as strong as ever for almost exactly one year now, despite long distance. We spend breaks in between college classes together and Skype often when separated.

Unfortunately, over the past several months, she has learned about the self-centered tendencies of my sister [15 F] and what kind of intolerable human being she is.

My sister has been making these visits notably unpleasant lately and reeks of jealousy that encompasses my SO's skin complexion, the fact that she is mixed-race, that she regularly talks to my sister's ex and even that she receives more attention generally around social media like Instagram and Facebook (my SO learned all of this through my sister's ex). He admits that she tried to hide her jealousy by openly insulting my SO.

To add, her ex has revealed to my SO that my sister trivialized my SO's depression and anxiety attacks; she complained to him that "[my SO] freaks out over nothing."

I would appreciate advice on how to break it to my sister that she's displaying disgusting traits and needs to make changes in her life before she loses all her friends and has trouble finding any dates.
<bot>: My sister is unhealthily jealous of my SO but masked it by outright insulting her and who she is as a person. How is this repairable?