I think I will be breaking up with my best friend and feel like I want to die

The actions of my best friend have changed significantly these few months. She constantly is in bad mood or what I don't know. She doesn't communicate about anything. If I hurt her about something she doesn't communicate and just keeps that in mind. She take so long to reply to my messages and sometimes just keep them on read... And she has been constantly making my mood bad and depressed. I have been crying everything because this same situation reminds me of the last time when I had a break up with my previous best friend. I am afraid the same thing is going to happen soon and I am not ready. I tell her everyday that please don't do these things. It makes me really sad and depressed. But she is doing that constantly. She gives reason like she is also having bad mood, etc these days. And when I ask her she wouldn't tell me. She is online on whatsapp but doesn't reply to me... When I ask her who she talks to she doesn't tell me and says they are not important enough for me to worry about. But still I get sad. I feel like I am not give priority over those less important people. It's mentally eating me everyday. I don't know what to do and I have emotionally invested in this friendship so much and I got no other friends as well that I am much invested into or feel a connection. I don't know what to do now. I feel like I want to die because everything is repeating. On top of that I am suffering from depression and it's actually making it worse and in no way I am able to deal with all these. I got no one else... I don't know what to do