Because her ass is very small.... like I said, that doesn't make it bad, it just makes it small. That image actually works against your cause since the hourglass shape refers to a woman's body shape when looking directly at her, from the front (or back I guess but the arms would make that look different since they are further back that the chest) while she is standing straight up.
Also, the power in your thighs comes from your quads (which are in the front of your legs) so "powerful thighs" is probably not a good descriptor for her legs in this instance. C'mon man, I though you were the authority on the human body. You can't go around, getting all aghast when people question you, then miss something as basic as this.
as a reminder, her vital stats and some quick analysis :
Height : 5 ft 5 in (1.65 m)
>> rather small
Weight : 125 lb (57 kg)
>> rather weighty
Boobs : 32JJ
>> outsized !
Waist : 27
>> not really thin
Hips : 38
>> not that small
WHR = 0,71 not exactly an hourglass shape...
what I would say is that she is a rather small girl with a reasonnable amount of excessive body mass (about 5kg) mostly distributed between her boobs and her waist.
with some regular fitness training she could easily improve her WHR.
now, some front pictures where you can easily see that 99% of her hourglass attributes are located between waist and boobs.
In fact she is a "half hourglass" or something closer to an "apple" shape...
her total bust size, assuming she measure her boobs in US unit, would be 32+11(K) >> 43
that makes a "Waist Boobs Ratio" of 0,63 which this time range into the hourglass shape.
focus on her ass : it's hard to find pics where she really shows it but as you can see it's rather flat compared to her waist