I'm still not sure. I really don't want to risk ruining such a good friendship.
And you shouldn't. She enjoys talking to you, not because she's romantically interested in you, but because you've been her friend for
5 years. She wants to travel with you because, again, you're such a good friend. You will meet thousands upon thousands of girls in your life. Which do you think is more possible, being able to successfully ask one of them out, or being able to successfully cultivate a relationship with them that lasts 5 long years? This is a good relationship you have with this girl and my opinion is that it would be very dumb to risk ruining the relationship like this.