@Puffer I have a size 37.
We found out that apparently most manufacturers rate their heel height at size 38 or so. This means that if you have a smaller size you'll get a lower heel and if you have a bigger size a higher heel, so the steepness is the same.
The Hot Chicks are a good example - advertised as a 130 mm heel (probably in size 38). In my size 37 with a 12,7 cm heel and in mlroseplant's size 40 a 13,7 cm heel.
I think your girlfriend was an exceptional talent in heels.
Her 14 cm heels would mean something like 13 cm in standard size, so like the Louboutin Hot Chick again. I was well used to high heels when I got mine, and yes I was able to walk in them from the very beginning. But it was not an elegant/comfortable walk in a way that I would've worn them out immediately 😉
And I've seen so many other women struggling to walk in something like a 7 cm heel.
So I think there is some kind of natural talent for walking in heels, and your girlfriend definitely had it!
Generally we here are already on the top end with anything of 12 cm+, considering that most people don't wear heels at all or only low heels.
There's also the other extreme - I remember a women modeling for Fuss-Schuhe (a german shoe brand/seller), and there were videos of her walking even in the most extreme heels. This was a big motivation when I got my Hot Chicks - if she can walk in 15 cm (?) heels I sure should be able to walk in 13 cm 😀