Go up and say hello to her, then improvise, ask her if she often comes to the library, ask her what books she likes to read, ask her what class she is in, then say that you also like reading and what books you read, and then say that you want to communicate with her! Be generous and sincere. Or, if you don't know how to speak, you can walk in the back first, then take the money, go up to him and ask her if he dropped it, so as to strike up a conversation with her and then say the above words.