I don't think you want to just show up and surprise her. I don't see any way that ends well. She'll figure you've been spying on her since she didn't tell you. It's a very personal thing and she has chosen not to tell you.
I hate to say this, and I hope nobody jumps me, but I think this is one of those opportunities for her to find out what life will be like without you at her side. And I don't mean that in any vindictive kind of way at all - nothing is scarier than finding a lump and then waiting to find out what it is. But reality has a way of inconveniencing people and we may not be there to cover for them. That's part of the consequences of choices, and so far she's choosing to leave you out of this.
For all you know, she may be testing herself here to see if she can go it alone.
But if she does tell you about it and invites you along, by all means go. Let's all hope it turns out to be nothing.
