It was already explain in early chapters that when they were born soul taker mistakenly swap the soul of Camilla and MC. And soul taker show them each others life through dream. The moment they realized each others presence their body swapped. It was condition to go to their own body.
Original Camilla was also a good person but because of all the mental torture she got from her family and peers, she somehow became twisted. And when that red haired showed a bit of kindness towards her she became obsessed with him.
My hypothesis is that the ogCamilla forgot her childhood memories or don't much remember about Laila because she was pretty obsessed with the red haired shit.
And if you remember MC told that Laila always wanted to be friends with ogCamilla. So it is just that ogCamilla doesn’t' remember her.
If Laila has known Camilla since childhood, why does Camilla bully Laila in the novel before Camilla's body is possessed by someone else? Does Camilla (OFL) really forget about Laila?I'm little confused actually...