Hi, Mor. Well, if it is still doubtful whether this matter pertains to human or divine law in the judgment of the Roman See, a few centuries ago, Pope Benedict XIV, a great traditional canonist, after a detailed study of the question remarked, "Communicatio in divinis (in divine/sacred things) with the heterodox cannot and should not be so readily and so generally pronounced forbidden in absolutely every circumstance (in omni penitus circumstantia). "[Source: De Martinis, Juris Pontificii de Propaganda Fide, pars II (Rome, 1909, pg. 324)]" Blessed Urban V also gave to St. Peter Thomas a clear permission to share with the Orthodox "in divinis", with the provision, however, that this permission did not extend to anyone excommunicated by name by the Holy See. Without approving of division, but making due allowance for the simplicity and good faith of the Christian faithful confused by the unfortunate hostilities that had sprung up between Latins, Greeks and others in the Church, Pope Clement VI gave Armenian priests a permission to administer Sacraments among the separated (See http://papastronsay.blogspot.in/2010/10/communicatio-in-sacris-vi-armenian.html
) There are other examples mentioned in the site above with references.
If you can commune with them, why specify "speech/conversation" and "meals" as also being allowed?
With regard to the decree of Pope Innocent IV, it seems to be a generic permission for Catholics to commune with non-Catholics in matters both secular and religious. What do you understand by sharing in offices? You would exclude public liturgical prayers? Beside the decrees of Popes, we have the teaching of several leading Cardinals, Bishops and priests; St. Robert Bellarmine, a learned Cardinal, knew and cautiously approved of the practice of some Catholic priests giving absolution to simple Christians unaware of the divisions in separated communities,"If the penitents say that they know nothing of the controversies, and if they really appear to be totally uneducated, then perhaps one can hear their confession". Rather than ask them difficult questions which they would likely not know how to answer either way, priests would ask them simply whether they believed all the holy Fathers have handed down, and were remorseful for all their sins. If they said, yes, they would receive absolution. Pope Pius IV approved a similar permission to the Jesuit Christopher Rodriguez and a Roman Congregation in 1643 told the Capuchin Sylvester that he could continue his practice of giving absolution to separated Christians who ask it of him on their own accord. At other times, Popes were more severe, usually when they judged there was some proximate danger to the Faith in some circumstances. But Pope Benedict XIV shows the general prohibition was not traditionally considered divine law applicable in each and every circumstance.
As for why she did not become Catholic, Mor, well, the reason the Bishop gave for finally allowing her to receive Communion was that she was "more Catholic than many Catholics". But I understand what you mean and I think it has something to do with the fact that formally changing one's religion - even if it is to another Christian Church - especially in secular society today, is not an easy decision for many and in some cases can take decades, or even be a lifelong journey. This is understandable and I think the Church is wise to patiently and lovingly as a Mother accompany such persons with unconditional acceptance as they seek to discern and do God's will, however long it may take them. Though the woman and her husband are favorably disposed to Catholicism (and generally toward Orthodoxy as well, like certain Protestants of the so-called "High Church" mindset) and would welcome a union that was agreed upon by the Bishops and pastors of the churches, I'm not sure if they will take the final step themselves. While all Christians, after prayerful discernment, should strive to be responsive to His grace and fulfil God's will as best they are able to know it, I disagree with Fabio Leite here and think personally that there absolutely is hope for restoration of full unity in Christendom and the better path toward it lies in Bishops and theologians from both our Churches coming together in synods or councils to discuss the doctrinal issues that remain and see if agreement in essentials (along the lines of In necessariis unitas, in dubiis libertas, in omnibus caritas
) is possible, as the Councils of Lyons II and Florence were convened to do and the like of which could easily be done - without many of the historical contingencies that complicated the situation at the time - in the decades to come.