Do you agree with Sophie's actions regarding helping Langdon so far? How would you feel after not speaking to Jacques for several years and then finding out that he died?

If I were Sophie, I would feel guilty for not speaking to Jacques for several years and then missing the opportunity to patch things up. However, I might also feel justified, in a way. It depends on what the, as yet unknown, act that Sophie witnessed was. If it was something horrible, I might feel slightly less guilty. Either way, though, if the man was my grandfather, I would hope I could have patched things up before his death. So, it makes sense that Sophie is now trying to help him after his death by assisting Langdon and finding Jacques' killer.