I might be stating the obvious here, but you need to know what things are deal-breakers in your book. If you never meet the other person, if you never meet her friends, if you never meet her family...what can you live with and what will eat away at your soul?
Also, be very clear and firm in what you need to be present in a relationship with her. Tell her you want to meet her other (if you do), or her parents (if you do), etc. The way she responds to that may tell you all you need to know about whether there's a looming expiration date on your relationship.
Be patient but not a pushover. Perhaps there will be a level of settling down from heightened emotions and feelings and sensations into a secure situation. Maybe the SO just needs some time to make sure she isn't off on some flight of fancy with you.
And the worst piece of advice of it all? Know when to say when and, if it has to be said, say it gracefully. I sort of wish I had rather than holding on to the "if things were different." Things only get different if she wants them to.