When all of the New Directions girls are lined up to get pills from Terri, there are two girls at the end of the line that are supposed to be Brittany and Santana, but they are not. This becomes increasingly obvious when, at the other end of the line, standing next to Rachel, is the real Santana! (at around 46 mins) The whole line of girls can be seen - seven total, with fake Brittany, fake Santana, Mercedes, Tina, Quinn, Rachel, and real Santana.
When Quinn opens her locker she simply turns the lock dial a little bit and then pulls on the lock to open the door. This is not how these lockers work. The lock has to be completely removed from the handle before the door can be opened, but Hollywood types believe such realism is a waste of time.
Terri says that the Pseudoephedrine products are "simple over the counter" items that you can get in the store with no problem. Actually, the US regulates the sale of pseudoephedrine products, limiting a person to how much they can by in the store. Most stores scan the license in store and it would prevent Terri from getting as many boxes as she did, unless she bought some herself as well.