Concentrate on the diminishing the waist through exercise and good eating, this will make you look much more curvy than trying to gain hips. I went from 32 -> 26 inch, while losing 1 inches 40->39 on the hips, since I've lost 25 pounds through HRT though better eating and light exercise. People keep commenting on it every single day, saying I have a model like figure, yet my hips DECREASED. Unless you've got very broad shoulders, I would always recommend decreasing the waist so the WHR (waist to hip ratio falls under 0.7). Most women over 30 have WHR ratio over 0.8 because they are overweight.
I would recommend building your muscle mass, the buttocks, upper leg muscles and core muscles are big and you're still feminine if you have them, lean one, not bulky, to up your metabolism. The body on HRT naturally will go for the fats behind the abdomen wall first which will have a dramatic effect on your waist.
My WHR ratio is lower than almost everybody my age, 26/39 = 0.67, most women with that kind of ratios are in their early 20's.
Most women who have large hips also have some weight around the mid section, so they are less curvy than they somebody with less than 0.7 WHR.
One thing that's funny, my mother keeps telling me I have no hips when I've got proportionally more hips than my sister. What makes them less prominent visually is because of my height. The distance between my waist and hips is much longer than a shorter women and so, the difference between them is not as obvious even when its greater.
Because my waist's small, I get some trouble with size 8 pants being fitted on the hips and buttock while being loose around the waist, size 6 is very tight on the hips and fitted at the waist. That's why I now buy 7-8 pants fitted below the waist or hip huggers since I never can find one which fits the waist and hips.