I don't really mess with yandere Sylvie... I assume full yandere is when she rapes you, she does a lot more ranting than the usual version of the scene. Sylvie won't really question you going out alone normally but yandere...
Talking before leaving Sylvie said a few things about how she could change for me to like her more. Tried leaving her alone a few times, occasionally Sylvie would demand a kiss before leaving. And there's the...
The first night time test I swear she mention Aurelia after, but I was clicking too fast and it didn't happen again.