Loki gives her a small smile. He's the last person to tell someone that despite their behavior in the past they're a good person now, and he expects that Abby would not appreciate hearing that in the first place. Her 'goodness' isn't really in question, here.

This is a matter of nemeses, and trust, and Loki still trusts Abby.

"You're welcome."

The song begins to wind down and Loki nods. "Do you want to keep dancing or should I leave it to the one tune?"