There was a post on here recently from a mother who mentioned she could not afford tutoring for her DC to help them with their maths. Lots of knowledgeable replies followed where MNs recommended online resources the DC could access for free to help.
Is there anything similar for Chemistry? DD sometimes struggles with new topics. Her whole class struggles; I believe they have the teacher who has high academic qualifications but is the weakest in the school for explaining difficult topics to their GCSE class. If there were a resource she could access online, that could help.