Comparative religion might be something she'd like.
Unfortunately, I can identify with the problem of having a DD that enjoys active/spirited discussion as her favored mode of education. It's problematic because it requires synchronous discussion with others thinking about things on a higher level than most of their peers do/want.
Online courses have been of limited value to us in that regard. the discussion there just isn't robust enough-- or, indeed, interactive enough.
A message board environment like this one is one possibility, though I've found that my DD is a bit intimidated by the wild west feel of the most active message boards, which tend to have light-to-nonexistent moderation driving active or highly controversial discussions.
