effects of hive minds.....but i got off topic

why do we let people push our buttons, get us worked up and cause uber drama? i have been having issues with a family member/ex-boss. i found out that she had been lying to my face and blaming me for every problem or issue at work. i always believed her when she told me that our supervisor was playing us against each other. then when i was transfered to another store (because she constantly bitched about me to the point that i was moved to shut her up) it was confirmed by three other people of what she had been doing. she was family, i believed her, i would have done almost anything for her. then found out that she did that to me for months. totally ruined any trust or respect i had for her.
now we had a disagreement on facebook. totally wrong forum and it was my fault for starting it there. however, it was between us and didn't have to spread through out our stores. the ripple effect of this has been tremendous. she has a habit of creating her little cliques that are almost a hive mind. if she is upset or angry with someone hey have to be as well. i had an employee who would not talk to me for weeks because she didn't like the way i had talked to her. and it just went on and on.
she has been texting me, calling me at work and posting on facebook about me. she had people telling her she should kick my ass, etc. my brother pointed out to me tonight that we were both acting like kids and that we are both in a dark place. i agree that we both "misbehaved" he recommended that we needed to talk. i tried to call and she wouldn't answer. she would text me but wouldn't call to actually talk it out.
someone told her that i called her a whore. i did say that she was with her significant other for financial reasons. i have tried ignoring her, avoiding contact with her. i didn't think it would be worth it to talk it out. she then said she was done talking. i haven't confronted her because i don't think it will accomplish everything, she said that i had been caught in a lie already but wouldn't tell me what that was. so i doubt it. i really don't lie to cover up anything i have said or did.
what i don't understand is if you have a problem with someone why do you need to involve others against that person. why do you make people choose between one or the other? do you not realize that someone can be friends with two individuals at once? all of your friends don't have to get along.