Most of the time people who are like that struggle with really bad depression or a developmental issue, I once knew this girl in my freshmen year and she was my best friend during middle school, she was the nicest most trustworthy person I ever met, then she started doing things like glaring at me, saying things that were lies and disrespecting and one that said the slightest thing it was the 4th month of that happening when we got the news that she had killed herself when we talked to her close relatives and friend they said she had struggled since the beginning of freshmen year, but no one did a thing for her. maybe the person who is doing this has their own issues going on, maybe you could try to be considerate of that, or ignore them whatever helps