Take her out for a coffee or something and straight up ask her what she expects from travelling with you, I know you said you never wanted to ask her bluntly but the only way to deal with this is to ask her bluntly so you both know what you're getting into on this trip.

It would be far worse if you pussyfoot around the subject rather than tackle it head on as simple things you could enjoy like getting coffee or sightseeing could be ruined by tension that can easily be avoided by communicating properly before taking the trip.

It doesn't matter if your relationship in the future is romantic or platonic, the only thing that matters is that you treat each other with respect and communicate with each other honestly in a way that lets you both know where you stand and remain friends. Hopefully you have a great trip whether that is with your friend or alone.

Good luck.