This must hurt pretty bad. Especially since you’re getting hit twice. The sudden cut-off of contact, as well as zero explanation as to why. The lack of closure can actually be harder long-term than losing the friend.
Since you didn’t have an actual question included, it seems like you might have posted this to get it off your chest. Which helps. It’s therapeutic. Writing organizes your thoughts and helps you see patterns which might lead to some answers.
Sometimes you find an answer, but you still won’t be 100% sure it’s the right one. But it’s close enough. Sometimes “close enough” helps you move on.
I’m going to riff a bit here. Hopefully that’s OK.
Losing a close friend can be more hurtful than losing a relationship partner. You might grow to feel safer around the friend because there’s no relationship baggage that adds this lingering cloud of doubt.
Four years for you. That’s long enough to feel safe with somebody. And plenty long enough for this to be soul-crushing.
Let’s say you are never able to talk to her again. You have two mental hurdles, beyond getting over the loss.
1. Figuring out why she cut contact.
2. Figuring out why she isn’t talking to you about it.
Why she cut contact. Odds are that it’s one of these.
--She was using you to feel better about herself and was done needing you.
--She was becoming attracted to you and that scared herself off.
--You did something bad that she considered unforgivable.
--You did something not-so-bad, she didn’t like it, and that annoyance grew until she didn't want to be around you anymore.
--Someone in your social circle said something negative about you and it clouded her reality.
--You fell victim to her BPD symptoms. For example, if she has black-and-white thinking, she could now consider you evil.
Anecdote.
I am male. My platonic roadtrip buddy was female. This worked because I made it clear right away, partly joking, that I would do whatever she wanted and never question it. I made good on the promise though. We were inseperable for five years. One day, she suddenly just stopped talking to me. Years later, I found out that she chooses specific friends to feel better about herself because she’s mentally incapable of having an actual romantic relationship. In hindsight, this makes sense because I saw her turn on her best friend and chase her away. Turns out my now-ex-friend really hates when her own friends date someone else. Her best friend now? Another woman, who will never bring a significant other to social events, because the husband has extreme social anxiety.
Figuring out why she isn’t talking to you about it. Odds are that it’s one of these.
--She’s incapable of this level of communication. (This is very common.)
--She doesn’t think you’re worth the breath, and might not want to give you the satisfaction of an answer.
--She thinks this is how life works.
--You fell victim to her BPD symptoms.
This is the first time it’s happened.
Another anecdote.
The first time I lost a group of friends, I was in middle school. I had to cut contact because they essentially turned into neighborhood thugs. That meant I had to find new friends for high school. Not enjoyable.
But that actually helped me realize I could do it again if I had to. And I did. Three more times.
My high school/college friends turned toxic, my resulting work friends were extremely toxic and my resulting giant group of social friends got so bad, I actually moved out of state. Yeah, I fled. (But I got a wife out of the bargain, so there's that.)
Interspersed with these episodes, I was rejected by numerous people who I considered friends or significant others. Some times, the closure came from me having to figure it out on my own. Other times I got the real answer from other people... .and the truth was so bad I wish I never found out.
All this left me jaded enough where I either had to give up on humanity, or understand the more-forgivable reasons why human beings act the way they do.
I chose the latter. But that’s another post.
-ngu