so who did you kill and who did you spare on your first run? the game easily baits you into killing toriel at first, it made many think that you must weaken her to prove yourself.. then a 300 crit happens and she dies.
btw if you reload after killing goat mom and spare her, this happens
this fucking game got me with this the first time, I wanted to make things right and got called out for it. genius
there is also a variation of this dialog if you kill the random monster encounters but not toriel, flowey says that just because they are not 'bosses', they are someone else's toriel, and calls you a brat.