Bez, I had two teenagers, a 3 or 4 year old and a 7 or 8 year old; I honestly can't remember the exact year! The older two remember it well, my daughter even being a "permanent" auxillary pioneer for a while. My oldest son had the most trouble, went back a couple of times before letting go of the guilt after taking off the blinders. The one that was 7 remembers everything vividly, the youngest, not so much. When the older girl decided to leave, the witlesses wouldn't let her be. They hounded her and she became terrified, asked me to shield her from them. That didn't last long.
You might tell your little one that her friends mom is a bit confused right now, you never know if/when she might change her mind. Try to keep your emotions out of it, be calm and rational. They pick up on our feelings. You'll fill her life with other activities and she'll have new friends. If you don't let it feel traumatic, it might help. Feel free to pm me and I'll give you my email. Mine are all so grateful!
Emma