Honestly it does feel like a cheap solution by removing memories, but hey, we aren't here to nitpick on too serious stuff in a science fantasy adventure so let's just move on to Shiki's new training arc.
I completely understand why removing her memories was good for her. Her Brother is able to handle his PTSD while his Younger sister really isn't able to.
Hell in Universe If you were her brother you'd want that shit removed too. I know I would have.
No, if it's gone it's gone. 'Resurfacing' is just a poorly-written drama trope when it comes to removed memory plots. If it was suppressed, it could resurface. If it is REMOVED then it is gone.
Either way, the point is her damage from the memory was preventing her from healing. Even if it somehow comes back, now she has the time to heal and grow stronger while it's non-extant.