Donald purposely did not tell Matilda they were coming, hoping to effect a reconciliation between her and Scrooge, but Matilda refuses to believe Scrooge is sincere and thinks he is only interested in the treasure.
Donald intentionally kept Matilda in the dark about their visit, hoping to smooth over her differences with Scrooge, but she remains unconvinced that Scrooge's actions are driven by a desire for forgiveness rather than personal ambition.