Using the platform, she firstly selects if she wants to borrow USDC, or BTC. This is very important. If Alice expects BTC to go up in relation to the other token (in this case, USDC), and wants to be leveraged that way, she will borrow USDC. If she believes that BTC will go down in price relation to the other token, she will borrow BTC instead. Alice chose to borrow USDC as she believes it will go up in price in relation to USDC.