I agree with most posts above. She'll wear them if she wants to. You cannot push that process too much, but you can give her reasons to want to. My wife wears her heels only and for no other reasons as to look good and occasionally to please me. You can give subtle comments which help her to see why it looks good. It took me 3 or 4 years to convince my wife that she really looked slim and attractive in those shoes/boots, and she never believed me until she lost a kilo and got promoted to management. Now she's wearing heels nearly every day to the office, because she thinks that it looks good under a business suit. She goes to dinners with clients and on business trips wearing nothing but heels, but unfortunately I rarely get to see her in it. When she comes home, the first thing to do is kick those heels off. If I ask her not to do so and give me some exposure as well, she says that she's tired after using them a whole day. I have very rarely managed to make her wear heels for no reason except for my pleasure.
Last saturday we went to eat something small in the city, and I asked her to wear one of her reasonably high heeled boots which she wears to work quite often. She said that she had nothing to wear with those! "What do you wear to the office then??" I asked. She replied that she didn't want to look like a business woman in the weekend, those are office clothes!! Aaarrghhh...
Anyway, after some begging and negotiating I got her to wear them, with a nice black skirt, just for me. Too bad the food wasn't too good ;(
So my advice is, that even the toughest partners eventually decide to wear something that you like just because they want to do you a favour, even if it goes against their wishes.
And I am aware that some of the readers on this board must think that I'm a nagger, as I'm always talking about my wife and her attitude towards her and my heels. But as that is my biggest problem what heels is concerned, I reckon it still is appropriate on this board.
And I have learnt something about women throughout the years

Maybe someone benefits from it.