My own default response to things like this is to go into "problem solving mode". Kind of a bad habit sometimes. I have a suspicion it's something you tend to do too. These days, confronted with situations that look like problems in need of solutions, I try to start out by asking myself what, exactly, the problem is and who's responsible for solving it. (It might not actually be my problem to solve.)
She talked me through more details about the night of the attack
Something to think about, maybe. I know there's nothing necessarily wrong with details coming to light as things evolve, but sometimes....... IDK, there's a type of situation where that happens.... I guess I'm not totally sure the what or why of it, but there are situations that evolve that way and it's not a good sign. Somewhere about the point you're at now, I try to realize that I should pause and ask myself "what else aren't they telling me?" Because you're probably dealing with someone who wants to recruit you to their side of the cause, rather than provide the complete facts of the situation and it's worth knowing the whole picture before you launch into Problem Solving Mode.
She described the letter as about 100 pages long,
That sounds a little crazy, for sure. Does she have a copy of the letter? Has she been officially notified of the debt collecting case? I guess I can't help but wonder why it matters, to him, what she used the money for. He allegedly loaned her money and wants to be repaid. If she used it to buy groceries instead of a laptop, would he be wanting the groceries back? If one of her house keys is missing, I hope she changed her locks.
But psychopaths do prey on the vulnerable. Indeed I recently learned from a moderator here that this forum doesn't have personal messaging and advises against meet-ups for that very reason, because it's happened here. Which makes me treat everything she says as plausible.
I remember when they stopped the PM function. I honestly miss it. I made some friends back then that are still friends, because we could exchange contact info through PM's. Everything comes with risks and benefits I guess.
Story that maybe relates to that, and may, or may not, relate to your friend's situation.
My ex-husband & I raised horses and it was pretty common to get a down payment, let the customer take the horse home, and have them make payments until the horse was paid off, then they'd get the registration papers. We sold a young horse to a nice young woman who was married and had a couple kids, one with cerebral palsy. When she picked up her horse, she asked us not to tell her husband what she'd paid for her. (Because it was more than she'd told her husband it was.) I told her I wasn't going to lie for her. That, if he asked, I'd tell him the truth, but I wasn't going out of my way to tell him anything, that was between them. At first, she made her payments on time. Then they were late. Then they were late enough that we reached out to her and there was always a story, but we got paid. At one point, after this had been going on for a while, she showed up at the house, at the end of what had been a longish day for me, with another story. She'd had the money, but got stopped by the police, with her son in the car, and was taken to jail, and it was all a misunderstanding, her husband didn't really steal that car..... While I was listening to all this, it struck me that the story was rolling quite easily off her tongue. Then a light came on for me. That was easy for her because she did it all the time. Basically, I worked for a living and she lied for a living. I told her that we were running a business and I couldn't go the the electric company with a sad story, they wanted money. I told her she could either pay for the horse, or we'd come and get her, end of story. (In reality, it would have been more complicated than that, but I wasn't sure if she knew that or if she'd take advantage of it if she did.) The end of the story was, after I blew up at her, we got paid. Promptly. So there was money available to pay whoever got mad at her first? I have no idea what, if any, of her story was true. Don't really care either. What I'm pretty sure of, now, is that there are people out there who make their way in this world by using people that way. And, it's turned out there are more of them than I suspected back then.
I'm not sure if people like that are involved in your situation at all. If they are, I'm not sure if you're dealing with one of them or two. I can kind of imagine what might happen if two people of that tribe tried to take advantage of each other...... The possibilities are probably endless.