Reply #8: You're not being rude by simply not replying to her e-mail. She will just

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assume that you never got the message, for any number of reasons. You need to decide right now whether you want her in your life again. If you decide that you don't want her, you should not reply to her e-mail at all. You don't need to explain anything. Just don't respond to any attempt to contact you. No communication = no relationship. If you reply even one time, you are opening the door again to her. It won't hurt her to not receive a reply to the message. She will just assume that you never got it, and will probably give up.

If you decide you do want her in your life again, I believe it will be difficult and problematic for you, unless you can "clear the air" about what happened with her brother. However, attempting to "clear the air" also might create problems of its own. She may not believe your story about what happened, the brother may deny that it happened, and things might even become worse than they were back when you were friends with her. It could become a "Pandora's Box" type of thing.

If you see some value to you in being friends with her again, then you might consider attempting it. But you clearly stated in your reply to my first post that "there isn't any benefit," so my opinion, based on what you have stated so far, is that you should not let her back into your life. What you do is your decision, of course. But if you decide you don't want to be friends with her again, then don't reply, don't explain, don't respond at all. Any communication you send to her can be taken by her as a invitation to become friends again.