That remains to be seen. She may have just let him go because she wasn't adequately prepared. A man accustomed to manual labor is undoubtedly stronger than a soft female librarian. She can't force herself on him, even if she wanted. Maybe if she got him really drunk beforehand, or drugged him with a sedative or aphrodisiac, or tazed him, or managed to handcuff him to her bed frame before his initial shock wore off, she could've accomplished her mission without Naruto's consent, but as things stood, there wasn't really anything she could do in that situation except give up.