Educational loans are guaranteed by the US government. When she defaults, Sallie Mae will sell her loan to the government and will be compensated 100% for all principal and interest.
The US government now owns a non-performing loan which they then sell for 10%-15% of what they bought it for to - you guessed it - Sallie Mae loan recovery. Since this loan can't be discharged by bankruptcy, part of every paycheck she ever earns will be garnished, every tax refund will be seized until Sallie Mae gets their money.