Answer:
1. Minimize interference
2. Meaningful material
3. Mnemonic devices
Step-by-step explanation:
In the first aspect, the sister should be advice on how to minimize interference, this include to try to study before sleep and also not to study two unrelated topics together. This means that, her brain would have cool down by the time she is ready for bed, and at that time everywhere would have become calm also, and she will be able to concentrate and assimilate better. Likewise, when she avoid the temptation of reading two unrelated topics together.
In the second aspect which is meaningful material, she should try to create image whether in her heart or on book while reading, this will make it to look real and help her understanding. Also, she should try to apply the concept to her own life, because it will help to understand very well too.
In the last aspect, which is mnemonic devices, this include the use of acronym, shorting the long statements to small words which will help her to remember easily. She can also change it to rhymes or story. All this will help her to remember what she had read.
In the sense, if she can follow these three steps her grades will be improved.