I like the idea of adapting the Braille - except it would be a lot of work, especially with beginner pieces (assuming she is a beginner), as she would move through these fairly quickly. However, if you used a fake book style - learning to improvise on patterns of the bass harmony - then you could use the textured stickers to represent different chords and read or memorise only the melody. This would cut down on the reading quite a bit while not making so much work (you'd only need a handful of patterns for any given piece, in most cases). It would also develop the improvisation side, which I imagine would be a relief when reading is a struggle.
At 14, I would be asking specifically for feedback about what works for her, and the techniques she uses at school. She could be very self-conscious, though, at 14 - but she would also be the expert at what works for her own reading.
Perhaps learning fewer pieces, but bringing out the most musical expression possible in even the beginner pieces, would be the best. But, don't stay on 'baby' pieces - make the biggest conceptual leaps between pieces that she can handle without getting lost.
I find that the Theme from Swan Lake is a really good piece for starting older girls on, as most of the intervals are by step - they can play this within a couple of weeks of starting music lessons. It makes them feel like they are playing something of real music without it being too difficult. This would also be good for this young girl, I think, as there is not much hand movement needed and there are two sequences in section A, with 2 in B (I think, off hand) and a return to A - but it sounds very beautiful. It is therefore very easy to memorise as well.
Annah