I was always interested in Art as a kid too, always drawing and making things. Just make sure she has a nice supply of art materials, pencils, pastels, paint, charcoal etc. You can get little art boxes to put them all in, like a little tool box. I loved my first art boxes. I'm sure she'll love experimenting with the different effects different materials can give.
I also loved going to the library and looking through the Art books and the Artists section, maybe a nice after school activity to do together.
I have very fond memories of going to Art/Craft Galleries/shops and Potteries with my parents. Seeing Artists at work in their studios is really exciting too something she may enjoy. Alot of areas have Art Trails/Open Studio's where local Artists studios are open to the public (maybe do a bit of googing for your area for this).
A sketch book would be a nice idea for her, in it she could draw, collect postcards, images from magazines, leaves/pressed flowers anything really that interests her for it's colours, shapes, textures etc.
You mentioned maybe visiting some Art Colleges, degree shows are open to the public, just look up the London Colleges websites for details.
Then there's New Designers which she would probably love as you have the best from all the degree shows in one place.
Hope something here is of interest to your dd