Parmesan
Anybody remember how in chapter 16 after Laura gets 'shocked' at touching C's hand and blanks out for a while, she mumbles about how it is a 'sin for her to love him' before desperately trying to assure that it is 'NOT a sin for him to love'? Perhaps after getting 'the touch' she also saw C's mental breakdown and eventual jumping off the roof. This might explain why Laura became drastically more obsessed to try and 'keep him safe' since now, on top of all the times he sacrificed himself to save her, she now feels partially responsible for C's misery. Thinking that her inevitable death (a key plot point) is what helped drove him to this point. If you think about it Laura has memories of all the horrible deaths she's experienced, the guilt of having C sacrificing himself repeatedly in attempts to save her and the knowledge that there is a high chance she'll die in few days, no wonder she went Yandere. Even without directly interfering, the system can still spit out Yandere's like a cowboy in a bucket factory. Anyway that's just a theory, a Yandere theory, thanks for reading! ( •̀ᄇ• ́)ﻭ✧