AITA for leaving a 15 year friendship die

Hi Charlotte and fellow potatoes! I've been following Charlotte for a while and have finally decided to share my story and ask you for your opinions since I'm at a loss and not sure what to do.

I (30F) and my ex? best friend (32F) have been friends since high school. Let's call her B. Over the years we have had periods on more or less intense communication, as I spend a decade moving around different countries. However, 3 years ago I came home for good and moved to the same city as B. When I moved back B was there for me. She helped me find a place to live, listened and supported me while looking for a job and we hung out quite a lot. And everything seemed perfect, as we were together figuring life out.

Now, there're a few things to point out about what has been happening while I was living abroad.

1. I have a house in our home town. (Different from the city we lived in when I moved back.) When COVID hit B and her husband found themselves in a difficult situation with no place to live and I offered then to stay in my house, while paying me a small rent, about half the market value. They lived in my house for 3 years.

2. At one point B's husband got a job that involved a lot of travelling and spending quite a lot of time abroad. B had never left the country at this point and was feeling quite lonely because of the absence of her husband. To surprise her, I got her plane tickets to come and visit me for a week and enjoy a proper tourist experience as I was living in London at that point.

3. We maintained contact for the whole time I was living abroad. We'd call and have long conversations sharing updates about our lives, sometimes more often, sometimes less, but never missed to share the important stuff.

Coming back to when I moved back. B and her husband had 'moved out' of my house 6 month before I moved back. The house needed some work and repairs and B and I agreed to go and fix some stuff together. We deep cleaned the house, painted one wall, fixed a lightbulb and it was all fine and fun. I would point out that B offered to help me with this, I did not ask her. However, while doing all this around the house, I noticed some stuff. Some things were in very bad condition as in not cleaned for a very long time, things were broken and just left, they had belongings still in the house, mentioned to have use the house after they had moved out because they were in out home town and it was 'more convenient', etc. I was quite annoyed at all this, but saw that there's nothing I can really do about it and as B offered to help me clean and sort out the house, I shouldn't be focusing on the negative.

At the same time, B shared with me that she's unhappy in her marriage and thinking about leaving her husband. We had many long discussions about everything that has had pilling up for her, how she's feeling, what are her options, how/if they can work things out. As he was still travelling a lot for work and we finally lived in the same city, we spend many evenings drinking wine and talking about things. I encouraged B to talk to her husband and let him know how she's feeling. She did and they eventually agreed to go to couples therapy. B really liked the therapist and had a few sessions on her own as well. I should mention here that B occasionally used substances when she'd go out to party or felt like she needed to relax. I had also done so with her a couple of times but fairly quickly found out I feel much better if I don't and stopped. Around the same time, after speaking with her therapist, B had decided that she needed a break from all substances as well, as she wanted to think her marriage through in a clear state of mind.

I forgot to mention that a few months after I moved back, while I was going regularly to our home town, I met my now bf (32), let's call him J. After about a year of living in different cities, I decided to move back to my home town in my house and invited J to move in with me. J is amazing and the best human I've ever been in a relationship with and we live happily together since.

About a month after I moved back to my hometown, it was Christmas and many people were coming back for the holidays, including B. A group of friends, again including B, had gone out one evening and invited us to join them in a bar. We, of course, went there to meet them and I was very happy to see B. At one point tho, in the middle of the evening B and couple of our mutual friends disappeared for a while and when they got back, it was obvious they had taken something. I was quite surprised, as I knew B wanted to keep a clear head and deal with her problems without using any substances but I said nothing, as the moment wasn't right to ask her about this. After a bit J and I decided to go, as we had a long day with his family and other friends and were tired. When I said that we're leaving however, B got really angry at me. She came to me and asked me in a loud tone if I'm leaving because she didn't invite me to join them on the 'fun' to which I said no and that I'm just tired. B was insistent there was something else and kept asking me why I'm leaving then and stood in my way blocking me from moving between the table and a glass window. I told her a few times that there was nothing and we had just decided to get some sleep as it was late, but she just kept standing in my way and was overall acting a bit weird (probably because of the stuff she took). At this point I got mad at the whole situation and told her that she looked ridiculous standing in my way and it seemed to work, as she moved away and J and I left.

In the next year we saw each other only 4 times. Once on my birthday, when J had prepared a surprise picnic for me and invited a few friends including B, once after that B came by my house to leave a gift from my birthday, once at a get-together of a common friend. B acted normally as if nothing had happened all times but I could feel that things were tense and weird between us. At the get-together B invited me and J to her birthday which was the fourth and last time we saw each other in person.

On her birthday, which was a weekend camping by the sea, it was obvious that me and J were in one way or another separated from the others and that B was taking substances again/still. B had told me a couple of times during the weekend that she'll come to me in a sec, or that she wants to come and talk me to me and see me a few times, but it seemed like she didn't really want to as somehow she didn't find the time for even one proper conversation, I was feeling off and out of place almost the whole time. Also, J had work and we had to get up and leave very early on the last day while the others could stay for that whole day as well. Before I went to sleep I went to B to say bye, as I knew she'd be sleeping when we leave in the morning. I tried to start a conversation a couple of times before she turned to me and I told her what the situation is and that I wanted to say bye now, as we probably won't see each other in the morning. She told me a quick and cold bye followed by an awkward hug. I told her to let me know when she's back, so we can talk/see each other, to which she said she'll be going to a festival after this weekend and doesn't know when she'll be back. I got that she didn't really want to talk to me and went to sleep. J and I left early the next morning.

Almost a year went by after this. At one point I decided to text her and see if we can pick up a normal conversation, which we did. We texted for a while sharing some basic news around us but B was travelling and the conversation stopped with me telling her again to text me when she's back. She didn't.

In comes another friend of mine and B's, let's call her M. M lives abroad and comes back every year for about a month. She's close friends with both me and B. M came back 2 months ago and spend some time with B, staying at her place, after which M came and visit me. M is aware of the situation between B and I and has been encouraging me to talk to B. When M came to visit I asked her about B, how she was and everything else M had found out while visiting B. To my utter surprise, M told me that B told her that she's sick of making all the effort in our friendship and if I want to be friends I need to make an effort. M knew that I had texted B and wanted to continue the conversation and she brought this up with B, to which B apparently responded that 'this isn't enough'. I was very much taken aback from B's words. I couldn't believe what she had told M. After M left, I sat with this information for a while and it just didn't sit right with me. I love and miss B, but at the same time I had given her roof over her head, had bought her plane tickets to visit me in London, had called her when I moved to my hometown numerous times to try and keep in regular contact while she never did, told her to contact me after her birthday and then again after her trip. She responded to none of that and then 'she was done putting all the effort and I had to reach out'? The more time passes, the more I think that B told those things to M just to had something to say and just doesn't care about our friendship at all.. At the same time, I am wondering if I missed something, if I was in the wrong and I didn't understand something... I haven't contacted B, as I just don't know how I feel or what to say at this point.

So, Reddit, AITA for leaving my 15+ year friendship just die like that?