Hit the titan again, fought a map battle or two and logged out. An hour later, logged back in and the game decided it wasn’t ready to stop the party and leveled her up again (to the same level she just did). Energies refilled, etc.
Maybe she unconsciously was not logged on her account when the first level up took place. You know, the thing where the Dark Lord appears warning us that our progress will be lost if not logged in on the account. That may be reason when your wife logged in an hour later, she is already in her account and was able to level up the second time. Curious to see her total titan hits.