I am not claiming that women reading at Mass is a violation of Canon Law or the GIRM. I wrongly attributed my observation of where it is forbidden for a woman to be if she offers the readings to Canon Law. It is the GIRM which a woman reading in the ambo/sanctuary violates. It's not what she is doing, it is where she is doing it.
#70 from the GIRM states:
"70. Laymen, even if they have not received institution as ministers, may perform all the functions below those reserved to deacons. At the discretion of the rector of the church, women may be appointed to ministries that are performed outside the sanctuary.
"The conference of bishops may permit qualified women to proclaim the readings before the gospel and to announce the intentions of the general intercessions. The conference may also more precisely designate a suitable place for a woman to proclaim the word of God in the liturgical assembly."
This references back to Liturgicae Instaurationes, no. 7:
7. In conformity with norms traditional in the Church, women (single, married, religious), whether in churches, homes, convents, schools, or institutions for women, are barred from serving the priest at the altar.
According to the norms established for these matters, however, women are allowed to:
a. proclaim the readings, except the gospel. They are to make sure that, with the help of modern sound equipment, they can be comfortably heard by all. The conferences of bishops are to give specific directions on the place best suited for women to read the word of God in the liturgical assembly.
b. announce the intentions in the general intercessions;
c. lead the liturgical assembly in singing and play the organ or other instruments;
d. read the commentary assisting the people toward a better understanding of the rite;
e. attend to other functions, customarily filled by women in other settings, as a service to the congregation, for example, ushering, organizing processions, taking up the collection."
What version of the GIRM are you referencing? In the current version on the USCCB web site and in my printed copy (2002), #70 addresses the form of the intentions in the Prayer of the Faithful.
Also note that Liturgicae instaurationes was promulgated in 1970. Canon 230 of the 1983 code supersedes the restriction against female altar servers; I don't know if the remainder of the document remains in force.