I live in Australia so the only Fashion and Textiles Museum is connected to fashion schools (I'm at a traditional, very theory based uni that's modelled on Oxbridge style unis - no fashion or design here unfortunately!)
I think I'm just worried because my resume and work experience so far has really been geared towards one area (fashion) and if I turn around and try to do something in art history they'll be asking questions about the sudden change - and it's really because I want to expose myself to other industries but will that sort of reasoning be considered acceptable?
I think it would be a bigger concern if you'd changed direction twenty times, because you'd probably change it again. They're not such radically different industries that a change of focus would be confusing...your reasoning is totally valid & interesting, so just make sure you can explain yourself fully and honestly