Try picking from any of these (Fa Zhou, as you recall, is her father):
Fa Zhou: My, what beautiful blossoms we have this year. But look, this one's late. But I'll bet that when it blooms, it will be the most beautiful of all.
Fa Zhou: I am ready to serve the emperor.
Mulan: Father! You can't go!
Fa Zhou: Mulan!
Mulan: Please, sir. My father has already fought for...
Chi Fu: Silence! You would do well to teach your daughter to hold her tongue in a man's presence.
Fa Zhou: Mulan, you dishonor me.
Mulan: You shouldn't have to go!
Fa Li: Mulan!
Mulan: There are plenty of young men to fight for China!
Fa Zhou: It is an honor to protect my country and my family.
Mulan: So you'll die for honor.
Fa Zhou: I will die doing what's right!
Mulan: But if you...
Fa Zhou: I know my place! It is time you learned yours.
The last two chunks are pretty simple to relate to your project's question as they show the events that led to Mulan's decision to take her father's place in the army.
sourced from:
http://www.imdb.com/character/ch0011756/quotes