Ex-friend reaching out after almost a year?!

So she was my best friend. I set her up with my brother, right at the get go I regretted it. My brother has been in and out of messy relationships, mainly due to the fact he was an alcoholic. But he had been sober at that point for over a year, was holding down his job, and paying his bills. He had never done this. So they hit it off, I think the fire burned too fast though. He wasn't far enough ahead in life for her or her parents, but she also wanted to be with him, they were on and off a lot, I asked her to either be with him for who he is or just let it be because I felt like the extra relationship stress he would start drinking again. He did btw.

She was at my house visiting and I asked her not to go see him but she did and found him drunk. I had a huge panic attack and cried over the phone and while our friendship was damaged I felt like we were still friends. I told her I know it wasn't her fault, and I knew it was my brother that chose to relapse.

My brother streams video games and she would keep creeping on his streams under various names but we knew it was her. My mom attacked her one day and after that my friend messaged me some hurtful things and I messaged her some hurtful things. I ended things by wishing her happiness in her life and apologizing for any harshness, and then I blocked her on everything.

It's been 10 months about since this happened. I've missed her a lot and have unblocked her on socials (still not following though) but I have been scared to reach out because I felt like she would hate me.

She reached out just a little while ago telling my that she wrote me a letter and it would be at my apartment in a week or so and that she hopes I'm doing well and she hopes I can read the letter when I'm ready.

What does an outsider think of all this? I appreciate you reading to the end. Would you engage in a friendship again? I would not tell any of my family members if I did decide to be friends again. Maybe she doesn't want to be friends and just wants to make peace, I guess I do want to be friends. Anyways, what's your take internet stranger?

Edit:. My friend is a recovered alcoholic. I told her his story and problems before they met. I admit that I put his good qualities at the front and in a way I understand now that was enabling. I am only 21 and grew up with a codependent mother and alcoholics everywhere in my family. I have a lot to learn I know that. But I refuse to accept that any of my brother drinking and their relationship is my fault.

Their first breakup happened because I really talked to my friend about how I realized he wasn't ready for a relationship and how I regretted setting them up. She wanted my advice because she was on the fence. But she continued to reach out and even reached out again just a few weeks ago to my brother. BTW I told her that day that his relapse was not her fault. I have text messages from months before telling her about my regrets and his negative traits. I did my best to correct my initial mistake, I told them how bad of an idea I felt it was and that I couldn't do anything at that point and that they were both adults and I was leaving it to them and whatever happened happened.

Of course I didn't want my brother to drink, but I've been around alcoholics my whole life and know very well that nobody makes them drink. It's their own choice.

There's more context.