For the sciences, it may help to remember that the grade boundaries are often quite low- she doesn't need to be getting 100%, so she doesn't need to know everything!
I would focus on key skills:
- Drawing graphs
- Substituting into equations
- Calculating percentages
- Practical skills including key terminology and how to write a method.
As these will benefit her across all sciences (and maths). Get her practising past paper questions, if you can, focusing on maths skills and practicals.
Seneca is really good for subject knowledge, and a lot of teens like it, but I would try to get her to do it on a computer, not a phone (less distractions).
I also really like www.savemyexams.co.uk/ for sciences- the notes are clear and visually appealing, and then she can practice the "topic questions" for that topic, as well (which are ranked easy/medium/hard). Unless she's aiming for 7+, I wouldn't bother with "hard" at this stage. Look at the mark schemes, they are often quite specific!
Is she just sitting paper ones for science? If so, there's only certain topics she will need to cover. If you're able to find this out, and the exam board, I'm happy to tell you which topics.
What's the aim for science? If it's to get a 5, would sitting foundation be a better option?