How should this monologue be acted?

The way to perform any monologue is to focus on what the character wants at that moment, what she is hoping to achieve by her words and actions. Take a look at the scene in which this speech occurs and think through what Juliet is experiencing. She thought she was all alone on her balcony thinking out loud about how much she loves Romeo. She didn't know that he was hidden in the dark garden below. Now that she knows he has heard her, she has mixed feelings. On the one hand, she's glad that he knows how she feels about him, and she hopes that he loves her in return. On the other hand, she doesn't want him to think that she's easy ("too quickly won").