A Member will earn:
i. Ten (10) base Points for each U.S. dollar, or the currency equivalent, that is incurred and paid for by the Member on Qualifying Charges
You may or may not receive the points / status credit for your stay if your sister pays. Which begs the question of why you don't just open a Marriott account for her and have her book directly. (or you pay and she sends you the money later)
If you have multiple rooms at the hotel and don't care about points / status, you could also just ask the front desk to move your folio charges to her bill.