It even looks good in IE6 (though the transparent png's could use the pngfix)
AOL the browser, or AOL the website? There's quite a bit of difference between the two.
It's the AOL browser that's causing the problem with the website you developed. AOL doesn't even offer the browser on their website any more--it was discontinued in 2006.
I see no reason whatsoever to do any development work for it.
But, if your client insists, then charge your normal development rate plus significantly extra (to account for the additional time, effort, and research for getting a website to work in a 6 year old browser). Once she sees that there is a price tag attached to it, it might help convince her that the browser is more trouble than it's worth (not to mention that it's a security risk to run a browser that old). If not, then you would be well compensated for your trouble.