Thanks for the report. In order for me to fix this issue I will need some additional information. Which route did you choose for Sylvia? Slave or Love route? Do you remember what Sylvia's level was at the time of this error? That will tell me exactly where the bug is.
All events should take into account where you are with every other character and change dialogue accordingly if there is need to do so, but this is a game in development, so there is still work to be done.