[That's a lie - they do, because they have a pretty good guess as to who on earth would call Flowey with something important enough for him to track Frisk down. But if someone died because of him, Frisk isn't going to let it go so easily.]
[Come on, Flowey. You've seen this determination before.]
Sans talked to me, too. He said someone got killed because of you.
[Action]
[That's a lie - they do, because they have a pretty good guess as to who on earth would call Flowey with something important enough for him to track Frisk down. But if someone died because of him, Frisk isn't going to let it go so easily.]
[Come on, Flowey. You've seen this determination before.]
Sans talked to me, too. He said someone got killed because of you.