Alan ,

You may have good intentions to surprise her with your visit.And you may be very sure , that she will like to see you - unexpectedly.

But there may be situations , when your visit is not at a good time.

i - She may be ill/sick
ii - She may work in another place (and can only come home for the weekend)
iii - She may not have her house/appartment in a state to receive you.
iiii - she may have relatives staying at her place

Is this your 1st visit to her and to that region ?
When this is your 1st visit to her , I surely wouldn't go to see her unexpectedly.

Other things to consider :

1 - she may have plans to go to the hair dresser and the manicure (but you came before that appointment)
2 - she has no suitable dress to wear ..... ( shoes , handbag etc )
3 - the family situation may not be suitable for a foreigner to visit her .
4 - on the financial part , she may not be able to present you with a nice good dinner and drinks , etc .

I would think it over very well , before going.
Just so it will not turn into a disappointment.

Anyway - Good luck