Tauriel hears his snores even before she sees him. Her steps check; then, she walks on. There is no way to act as if she had changed her mind without Frisk suspecting her, for they are a very bright child.

Blast Sans! She had wanted to give Frisk a moment of peace, and now he must take even that from them.

Her attempts to speak fall to nothing. She will let Frisk find Sans on their own time.