Should I stay friends with my bff or not? Please please helppp :P?

VERY LONG STORY!!! ok so I met my bff like a lil over three years ago at my grandma's house and when she and I started hanging out my grandma told me that she was surprised that we were friends seeing as she used to have a nasty attitude...well I never saw her "attitude" and she eventually became my bff...well recently she has been actin kinda weird and talking about suicide and the like and I tried to help her and coach her thru everything but I'm beginning to think that she's just talkin out of her you know what...so she's been in a really terrible mood and hates the world and everyone in it and I keep coaching her and giving her advice but everytime I look at my phone she's textin me bout how she hates this person or she hates ppl in general or life or what have you...so I got a job an naturally have less time for her PLUS her negativity brings me down so I kinda avoid her and she started noticing and called me a b$&?! and when I ignored her text she called me a b!?&$! again and again and then she'll say sorry and then she'll call me a trick and then she texted me beggin her to be her friend since I'm basically her last but I pretty much have been ignoring her for close to two weeks...she e called my phone and left a voicemail inviting me and my bf to hang out with her on her bday...what should I do? I feel kinda bad for her but at the same time she crossed the line when she called me out of my name and I don't respect her or see her the same anymore...HELP?! should