A few ideas….
For the rhythm side of things, I used to be a dancer and do dance competitions, and I remember at competitions, there was this deaf girl who was the most amazing tap dancer! And I asked her how she could hear the music and she said through vibrations in the floor! So maybe you could try something like this…. Get your student to touch the speaker so she can hear vibrations and chose a song with a really defined kick and snare sound – as the kick will often play on the one, and the snare on the other emphasised beat in the bar. Maybe if she can combine touch recognition with some knowledge about how drum beats work it could help? Sometimes people don’t even realise that you can usually count 4 beats per bar, and that usually something will indicate when the new bar has started. I once had a student who was really struggling with rhythm, so I found a song with a really awesome distinctive, repetitive drum beat (I chose Eple by Royksopp – this has a slightly more complicated kick pattern though, so you could choose something even more simple). This has no vocal melody, so we only had to focus on the grove. I just got the student to do a hand movement to every “1” beat. And then I added another hand movement for the snare, and before long she could find the beat in the whole song. Then we talked about noticing how the chords and melody also changed on every “1” beat. Maybe something like this could be cool?
As for lyrics, I remember learning in highschool psychology that we learn things better by associating the learned thing with other information; that’s why mnemonics work! So you could try to talk about some things to associate the lyrics with so that they stick in her memory better. You could start by talking about what the lyrics are discussing, what they mean, what story they’re telling (semantic memory). How the story changes in verse one to verse two etc. You could use other information too, like noticing if there’s a certain rhyme scheme or alliteration. Talk about how these sounds make the same mouth shape (physical memory). Maybe taking the time to talk about the lyrics could give her more to hold on to?
I’ve got no idea if either of these things will work but could be worth a try!!