After having seen the last screenshots on WIP, I think Chloe doesn't catch her mother with MC in flagrante, but to another couple. What happens is that at the beginning she imagines them doing it; as when Nicole imagines that she is sleeping with MC after her passionate fuck in her bed, terrified of the repercussions that would be if MC had fallen asleep next to her, until she finds that who is sleeping next to her is her husband John.
However, there could also be the possibility that Chloe caught them in flagrante but some magical action by Marilyn made her forget those moments or imagine them that they are another couple.
PS: Could someone recover the screenshots whose URLs have been lost of the first preview Earth-Child of Part 5?