Hello bikedreams,
welcome at Stridaforum 
Sadly, the online information about the suitable riderās heights cannot be taken seriously, Iāll try to explain why:
-
This information is for 16" and 18" wheels equal - that cannot be.
There must be a difference of around one inch (2,54 cm), because the radius (equal to the distance between the axle and the rimās edge) of the 16" wheel is one inch less than that of an 18" wheel. -
I wrote at point 1 āaroundā, because there is also a difference in the tyre width (and therefore the tyre height).
18" tyres are usually 1,25" (Schwalbe Kojak, Panaracer Minits Lite) or 1,35" (Schwalbe Marathon, Innova) wide,
in contrast are 16" tyres 1,5" wide - thatās not much, but it should be recognized. -
The third difference can be found inside of the seat moldings,
surprisingly does the QR seat manual mention the same range like the standard seat molding - Iām sure thatās impossible, too.
Weāve below a standard and a quick release seat molding half, the arrows mark the topmost (green) and lowest (red) position of the seat pinā¦
(Please imagine the seat pin on QRS as the blue line.)
The 163 cm claim is obviously from Vanmoof:
http://vanmoof.com/shop/catalog/product_info.php?cPath=112_113_131&products_id=178
http://vanmoof.com/shop/catalog/product_info.php?cPath=112_113_132&products_id=159
Ah, excuse me, what? 
Your dealer would sell you two Stridas and he wants extra charge for the adjusting of the saddle height?
Thatās an outstanding customer service, hmm? 
Standard seat molding adjustment, short version:
- Unmount saddle
- Release 3 hex bolts (in case of rear carrier 4) and remove seat molding
- Change seat pin position
- Undo points 1. and 2.
(I bet I can do that within ten minutes, and Iām just a customerā¦)
Iāve asked my friend Mike, accidentally folding bike dealer http://www.dasfaltrad.at/, about his opinion, he told me:
āIād never charge a customer for such minor adjustment if I sold her(him) the bike, regardless of the date of purchase.
Of course, if (s)he bought the bike elsewhere, (s)he will be charged.ā
Thatās contrary, Iād say - trust Bill 
I think to know whoās your dealer, as I do not want to offend somebody here, would you please answer your private mail?
Furthermore, maybe itās helpful to measure the inseam length of your better half?
Finally, 18" wheels, 1,35" tyres, QRS molding in lowest position and a ruler:
1024x768 pics are in this album.
