What is non-biased? If something you read doesn't comply with what the Catholic Church teaches, the Catholics will say it is anti-Cathoilc or biased against them. If it is against the Orthodox faith, the Orthodox will say it is biased against them.
It is really hard to weed out the polemics from actual theology, given that there has been a long history of just proving the other guy wrong from both sides. One book I read, "The Primacy of Peter" which is a compilation of 5 Essays on the subject and compiled by John Meyendorff (he also penned one of the essays) did point to that fact that the problem with the question on Peter's (and the Pope's) primacy is that both sides have resorted to polemics for such a long time that the Catholics would interpret anything and everything remotely related to Papal Authority to mean just that, and the Orthodox would distance themselves to anything that can even be remotely attributed to Papal Authority, to the point that some would even deny that Peter himself had any type of leadership role within the Apostles.
I guess the best way is to have her read books which focuses on Orthodox spirituality without having the jabs some authors take against Western or Roman Catholic spirituality. The worst thing for anyone really is to read something that tells them what they have believed all along is wrong.
