Only now does she remember that she's connected to others, that what she does hurts others, and that they hurt because they really do care.

Why now? Is Marisa relenting in her anger and apologizing because this is her last chance, or because Reimu's determination regained her trust? A little of both?

Either way, Marisa finally turned a corner. She let go of her anger and allowed herself to grieve. After she grieves, she can achieve acceptance, and move on with her life.

But if Reimu erases her memories now, that invalidates the entire process, and prevents Marisa from learning or growing from the experience. It will LESSEN Marisa.

Red_Inugami said:
Only now does she remember that she's connected to others, that what she does hurts others, and that they hurt because they really do care.

Why now? Is Marisa relenting in her anger and apologizing because this is her last chance, or because Reimu's determination regained her trust? A little of both?

Either way, Marisa finally turned a corner. She let go of her anger and allowed herself to grieve. After she grieves, she can achieve acceptance, and move on with her life.

But if Reimu erases her memories now, that invalidates the entire process, and prevents Marisa from learning or growing from the experience. It will LESSEN Marisa.

For some reason, I think Marisa should visit Silent Hill. Good place to face the truth, understand what you did wrong, and where you failed. Also, I'm curious about what kind of monster she'll see.

...maybe it's is just a way we east-Asians think(I'm Chinese actually), to us, having one's erased and created is somehow almost exactly as erasing one's existence; being more serious than death, which we commonly believe to be followed by an afterlife.
like pacing through the minutes before one's death, it's just natural for us to utter our innermost feelings to whoever nearby in this situation; and I sees this to be the case

I think most people would see erasing one's memories as a sort of death, but it's kind of hard to speak for an entire culture...

As someone who has dealt with depression personally quite a bit, I can say that what's making Marisa say all this is hearing Reimu say that she hates her. Depression alters your perceptions HEAVILY. You may even realize this during the process, but it doesn't change anything. Everything just becomes very, very dark, and your mind works wonders to make up reasons and excuses to make sure you keep seeing the world it wants you to. No one was able to successfully converse with Marisa because they were on separate worlds. No feelings could possibly get through the barrier Marisa's mind had set up around her.

Reimu saying that she hated Marisa broke everything down, because it was the first time the outside world matched the world her brain was trying to make her perceive. This whole time, Marisa had been twisting everyone else's words to make them seem ill-intentioned, as if everyone was just pitying her, but the fact is, some part of her KNEW that that wasn't the case. Some part of her sat there and watched herself say horrible things to everyone, but that part of her was too delicate to break through the barrier her mind set up. Reimu saying that she hated Marisa KILLED that part of her, that hope within her, and confirmed for her that all of the shadowy things her brain was trying to make her think were true WERE actually true. And because the outside world now matched the world only Marisa could see, there was no barrier that she needed to pass through. This is her, speaking honestly for the first time since her suicide attempt.