@Theredjellybean I would advise your DD to look into switching from Chemistry to Psychology (if she is doing Biology and Maths). Although Chemistry is the most often required A level there are about 12 which don't require it. The amount of chemistry in the course varies massively, at St Andrews, where DS1 is, it is very Chemistry heavy, but they require Chemistry, and he loves it. At Newcastle, Sheffield, Leeds, Lancaster and many others they don't require it. I think Plymouth requires Biology, but not Chemistry. I can link to the list on TSR so you could see how many doors that choice would close.
DS's GF got all 8/9 at GCSE and was very diligent and interested, but got a D for Chemistry A level so is now doing nursing instead of medicine. If I had known her earlier I would have advised her to switch.
The most important thing is getting AAA, although I think Sheffield accepts a B in Chemistry with an A/A* in EPQ but others are less flexible about where the B can be.
It was about this time last year that DS2 realised he wanted to do medicine, but he was doing double maths, Physics and PE. He dropped F Maths and took up an EPQ and is doing Chemistry Y12 as a Y13. He has now realised that he could have switched straight into Y12 Chemistry, so would have been doing Chemistry A level this year and would have a much wider choices of places he could apply to. Catching up with 1 term of another course is perfectly possible.
I think struggling with a subject you don't enjoy and are not doing well in is worse than working to catch up on a subject you enjoy. And it doesn't have to by psychology, if she is doing Maths, it could be Biology, Maths and Drama, Art or English.....