How do Sophie's motivations seem suspicious, in Chapters 11 through 14?

Sophie is very helpful to Langdon so far. She tells him that he is the prime murder suspect and seems genuinely interested in his welfare. However, Sophie also tells Langdon that she is Jacques' granddaughter, causing further mystery and suspense. Also, Fache receives a call from the cryptology department where Sophie works, saying that something is not right. So, Sophie's motivations are questionable.