I’ve been in a very intense and enjoyable relationship which lasted for almost two years. It was mostly a LDR, but we’ve spent a few months together in person as well (it’s been hard due to corona), which sealed the deal as the in-person and physical compatibilities were also amazing, and we enjoyed every moment together.

At the start we helped each other a great deal emotionally, unraveled each other’s issues, helped each other heal and bloom, become confident and full of life. It was a truly amazing experience to spend every day together, never a boring or dull moment, and the feelings, attraction only kept growing stronger. This has been going strong till the last few months.
We also decided to live together, marry and all that business. The plan was for me to move to her country where her house is being built and I have also participated in the that process as she constantly inquired me about the design, furniture and all that jazz.

My legal and economic situations are very convoluted though and so the progress has been slow, nevertheless we had the plan B or simply marrying to get me out of this swamp.
She did voice concerns about things being slow, how much she missed me physically, but we still kept going on and enjoyed every day together. Rationally, there wasn’t much to worry about besides things takes a bit longer, and there was always the plan B to fall on. Our feelings were unchanged, in fact they kept growing stronger.
Likewise, we engaged in many activities together, even a mutual project. Simply put, we connected very well on most levels and could enjoy each other’s company even while working.

Now, enter the third wheel. A “friend” I’ve known for a long time, became jealous and angry about her “replacing” him and began to project all sort of delusions onto her, such as her being a pretender that will only harm me, will tear us two apart and so on (ironically prophetic).
He became rather nasty with her, treating her like a lesser being. She had suffered a lot over it, cried a lot. I was intent on cutting him off since he simply refused to reason, apologize and own up, instead he kept doubling up on his abuse of her and made me lose more and more trust in him. Meanwhile, she kept wanting for things to work out, didn’t want me to lose an old friend, and so I kept trying to mediate.
The absurd thing here is that despite her being very aware of the situation and constantly voicing that interacting with him does her no good and that she should stop, she still kept doing it on and off, coming back bruised and in tears every time.

Eventually I had to cut him off from her and took the battle to our internal front as to remove her from the strife. Things were peaceful for some time.
As things didn’t really improve in between him and me, at a point I decided to simply cut him off as that’s not the kind of the friend I want. Needless to say that he didn’t take this well.
It seems like she contacted him again after this, or he did. According to her, she always felt some sort of unexplainable empathy and draw towards him. I must say that he also endangered my livehood, and she was aware of it.

This was the tipping point. Over the course of a few weeks, she did a complete 180. She forgave all the harm he caused to her and me, began spending every day with him and also turned against me, now parroting his hatred against me. She also shared my secrets and our relationship details with him.
Swiftly she turned me, somebody she wished to spend her life with, into an enemy of sorts. I have endured weeks of gaslighting, emotional coldness and generally shitty behavior as she became almost a different person.
We used to discuss everything in depth, analyze things, listen to each other’s feedback. Now everything was different, she refused to explain anything, became abrasive with me and so on. She also plainly said that he now matters more to her than I do, after talking for a few weeks!
This is also when her strong feelings towards me suddenly became to “fade”, as she said. She was confused and vulnerable, and decided that we need some distance so she can figure things out. The distance didn’t happen though, instead she spent every day talking to him and pushing me away more and more. I am more than sure that he played a big part in tearing us apart, as he himself confirmed when we spoke. She was vulnerable and he most likely took advantage of her to get back at me.
At a point, he even wished that I died.

Eventually, and after a few weeks, she broke up with me and wasn’t able to give any coherent reason as to why. It was always a “I don’t know myself”, “it’s how thing are”, etc. However, she denied romantic involvement with him, saying that she doesn’t know what’s going on exactly, meanwhile he kept saying that they’re falling in love.
Now, this is called overlapping and is basically a form of cheating, getting involved with somebody (who abused you for months) while still being in a relationship.
She also went back on all her words and promises, including helping me and wanting to remain friends. All of which were set in place before we got involved romantically.

We were still in contact though, but she became more and more abrasive over the next days, getting to the point of angrily snapping at me over little things. Then the gaslighting doubled up and all sort of accusations were flying towards me.
At this point, it wasn’t about her, me or our relationship but him and me.
I should also mention that he hasn’t shared this with her friends and has been avoiding interacting with them, being obsessed over the guy instead. When we were together and even though we spent most of our waking hours with each other, she never neglected her friends and always made space for them. I do know that the guy can be very controlling and possessive, as I have dealt with it many times.

Eventually I decided to stop talking to her for some time, so she can maybe cool off, figure things out and snap out of whatever charm he had placed upon her, or she placed upon herself as a way to cope with the situation. It’s been some weeks since when and we haven’t spoken. She hasn’t cut contact or removed me from anywhere though, but did ask me to retreat from some shared spaces which were important to her because seeing and interacting with me made her feel very sad over what was lost and how much she loved me.

I should also mention that she’s been extremely unbalanced during the whole ordeal, going from affectionate and rational to abrasive and angry. Likewise we also had days while she engaged in conversations and listened to me, and others where she refused to engage and instead attacked me.

She did mention feeling ashamed and angry about herself, which made her want to push me away when she actually needed me close.

I still love her strongly and care for her, but I must admit that I can’t really trust or respect her anymore, and I did a whole lot before this happened.

TLDR; Girlfriend of almost two years whom we made plans of marrying and living together with, dumps me for a bad friend of mine which I cut off who abused and made her cry for months, after talking to him for just a couple of weeks. She has a history of being stuck in abusive relationships.

Any insight is appreciated because I am truly lost. All of this is both extremely painful and absurd, and I can’t stop worrying about her being in manipulative hands either. Thanks!