Almost everyone gets nervous before talking to someone they find attractive. You don't need to remove that feeling. You just need to stop letting it decide for you.
Lower the stakes
You aren't asking for a relationship. You are having a short conversation with another person, and it can end pleasantly without leading anywhere.
Practice in everyday settings
Talk to more people in general: shop staff, neighbors, people in your class. Conversation gets easier when it isn't reserved for moments that feel high stakes.
Question the story
Notice thoughts like "She will think I'm a creep." You can't read her mind. Respectful, friendly conversation in an appropriate setting is normal.
Respect her response
Confidence includes accepting a lack of interest gracefully. If she seems uncomfortable, say goodbye and leave her be.
Count the attempts
Judge yourself by whether you tried and were kind, not by how she responded. You control your effort, and that's the part worth tracking.