This is the WCAG guidelines for making accessible websites (
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Honestly it's really more a "less is more" kind of thing. Have them turn off css and javascript and if the website still generally speaking makes sense in terms of ordering and the like she's probably headed in a good direction.
If they're on a Mac have them turn on Voice over and listen through the website. See if they can navigate around via keyboard.
Trying to add too many "features" can make a lot of accessible software not work, keeping it straight forward and not trying to reinvent the wheel is the best way to go.