"The former member is effectively foreclosed from changing her beliefs or taking issue with church authorities.."
Let me play the part of "a clever lawyer" to bridge the gap between this point and the idea that the right to religious liberty of the indivudual supersedes that of the religion:
Organized shunning (or "extreme shunning") effectively squelches the FREE SPEECH of the individual, but not of the organization or its leaders. The First Amendment protection of religious freedom is an extension or consequence of it's protection of free speech, not the other way around. That the founding fathers were concerned primarily with the inalienable rights of the individual is evident in the wording of the entire bill of rights.
For a religious group to claim First Amendment protection for its right to alienate citizens of their First Amendment right to free speech is a most perverse concept. I would love to embarrass them on this issue, but they forbade me from pursuing the higher education required for admission to law school.