The reason for Rosetta not knowing to ride a horse wasn't that her parents didn't allow her to ride a horse. Most of the vampiress from her society knew to ride one.
When Rosetta was young, a horse in the stable had kicked with its hind leg so hard that it had left fear in the back of her mind. Which was why, since that time, she approached horses with caution.
On the other hand, Alfie stared at Rosetta. The Marchioness would dip him in boiling water, if something bad happened to this young vampiress, once she would find out that he was the one to get the carriage around. He said,
"Milady, I don't think it is safe to ride a carriage by yourself. It would be best for you to wait—"
"Rubbish! How hard is it to hold the reins? I have waited all my life for this moment," Rosetta said to him, "I am seizing this moment. If someone asks, you can tell you don't know. Now how do I get this thing moving?" She asked him with a straight face.