Her Reputation
Elias' sarcastic tone was very discerning. Leonard could vividly hear the threat in his voice and he didn't know whether to answer the young lord's question or ignore it. What Elias said was the same consequences that Leonard had thought would befall Alice if she were to accept the engagement.
Her reputation among the nobles was already at the bottom and becoming Prince Revaz's fiancée would only make it worse. Then again, when Leonard thought about it, his master's arrangement would indeed make it hard for the enemy to approach Lady Alice again. So, the decision wasn't without reason and wasn't completely a disadvantage for the lady.