As a cleric of Shar it is normal that she does not like Selune and nobody likes githyanki.
No idea how this can kill her.
Well, unless Shadowheart joins your party,
she'll eventually be driven crazy by her box and try to attack your party.
But if your main character is githyanki, she flat out refuses to join and you'll have to persuade her. By comparison, Lae'zel might dislike anyone who isn't a githyanki, but she will join forces even a tiefling, because she acknowledges that alone the chances of survival are less. That is pragmatism.
