Losing the Plot (Mel Beeby, Agent Angel)

Second book in the Angels Unlimited fantasy series.

Once Mel was just an ordinary teenager. Now she's a time-traveling angel. When the Agency sends her and her two best mates off to sixteenth-century London to rescue a troublesome teenage trio, Mel has to wonder if they're worth the effort. What's so special about these three? Then disaster strikes, and Mel had better act fast.