You had accidentally broken Marybelle's fence. Her horses went running. She rounded them up before you could even try and help. She gave you a death glare. This wasn't the best impression to make on your friend's sister.

Marybelle: "You ought to be more careful! I can't afford to lose any of my animals, you hear? Good. Now get yourself in the house, and we'll have a little chat." The scowl on her face was intimidating. You were on thin ice.