Yeah, no. Serini was
1. evidently aware that she had no business being anywhere near Dorukan's and
2. clearly in no contact of any regularity with the wizard, given that she learned about his death more than half a year after the fact.
Further, by his own admission, Girard withheld the coordinates of his Gates from all Scribblers excepting Serini. Those explanations of yours don't quite add up and "there was an Oath, but most Scribblers played loose with it" explains what we've seen so far way better.
Well, Dorukan's Gate blowing up (which she would notice sooner than later) had a tendency to prompt such investigations. The Guard did their own as well.