[@Ardent Dawn] Both could make sense, but it seems Lugia is more important to her right now, for reasons we don't know yet. However, something was made mention as far as "atoning for past mistakes", and trying to find a legend that fits that, the oh-so-important mission, and a Lucario named Solomon is a major challenge.

I'm going to guess Celebi for now, as its Psychic Typing and the fact that a number of Lucario can speak through telepathy could mean the two could communicate without anyone overhearing despite the different types.