I get the sense that, again, you are way overthinking this. You do not need to take AP chemistry. Haverford knows what your school offers you. You are in already. They don’t expect you to come in with AP scores, which don’t give you an advantage in terms of your ability to learn new material.
Haverford is going to have a lot of support should you find chemistry difficult, which you may well do. The knowledge you will need to major in biochemistry at Haverford, you will get at Haverford. A Haverford prof isn’t going to use AP chem as the basis for his/her curriculum.
The whole point of a placement exam is to see which level of class is suitable for you. You don’t need to “do well.” You need to be in the right level of class. Study for the AP chem exam if you like, but honestly, self study is nothing like being in the actual class. FWIW, my D self studied for an AP and got a 5. She decided to enroll in the 100 level class because she didn’t feel her own study was thorough enough. She was very glad she did. AP classes are not the same as college classes.
By the time you graduate from Haverford, you are going to know what you need to know to have a great degree in biochemistry. No need to put the cart before the horse.