HR should absolutely NOT hire family members!!! Ever!!!!!

I work for a very small company and HR consists of one woman. Her minor daughter has been working in my department for the summer and she has literally ruined everything. It is insane how much she complains, talks shit, and snitches to her mom. I've already been annoyed with my now former "work bestie" constantly oversharing and talking shit, and now she and HR's daughter have teamed up to go all these extra steps to avoid me and treat me as if I have a deadly contagious disease with zero explanation, but most likely because I showed too much frustration about something. Totally shouldn't have done that, but their shit talking, trauma dumping, and now excessively petty behavior aren't very nice either. I hate how hostile my work environment has become, I hate my higher ups for allowing conflicts of interest (the CEO's son works in my department as well), and most of all I hate myself for letting this immature bullshit get to me.