Actually, that’s not a bug. There’s two key parts to the wording of the hero power:
1.) It says “next battlecry” but not “next battlecry this turn.” This means that she can use it and, if she doesn’t play any battlecries that turn, the effect will carry to her next turn.
2.) It says that the battlecry will trigger “an additional time,” not “trigger twice.”
This, combined with the fact that it can carry over from a previous turn, means that she can use the hero power, not play any battlecries for that turn, then on her next turn use her hero power again, and now her next battlecry will trigger two additional times, one for each hero power use.
Looking at the history log from your screenshot, that’s exactly what happened.