What you seem to be failing to take into account was that she had agreed to lend it to him, then failed to clearly indicate exactly when she wanted it back.
"I should be going now". Now means NOW, not later, not tomorrow, N-O-W! Followed by 'I need to go home'. Looks like she was politely asking him to stop so she could leave. The 90 second delay was probably because he had to have his Big-O before he'd stop, so he probably didn't hear her mention her need to go home now. jmo