Moment to moment awareness conditions a lot of our relationship with the body, and speaking as someone who has experienced depersonalisation, a great deal of the time I think it's due to an inability to accept certain elements of the 'content' of those moments that creates the detachment that leads us to feel disconnected from the body.
Unwillingness to confront emotional aspects of one's everyday reality can manifest as fantasy, of which the complexes involved in anxiety are a subset. Rumination over the past, an impatience with the present, and projection into desired or feared future scenarios all can pull awareness from that less than ideal present, and once developed into a habit, depersonalisation can be an extreme result.
Personally I have found the Buddhist loving-kindness meditations to be extremely helpful. Superficially, it seems to be a wishy washy feel good bland sort of thing, but past the more shallow presentations of it, metta-bhavana has more profound aspects rarely articulated. The practice usually goes something like: think of someone you love, and feel a genuine sense of warmth, love and compassion for them, a friend, family member, etc. Once you have generated this feeling palpably, then move onto someone you like a little less, then someone you like even less, until you come to people you feel little of anything for. Past that is where it can get interesting. You then focus on people you find casually irritating, and then people you've had confrontations or more significant problems with, and try to generate the same level of compassion and love for them. Bland, simpering compassion works, but as a creative exercise, it's worth trying to find a perspective on the person in which you feel genuine, authentic kindness for that person. The practice is then extended to larger groups of people, the world, and eventually, all sentient beings.
Superficially, the practice is about being nicer to people. The effect it ends up having is rehabilitating one's relationships to mental objects (including one's perception and experience of the body) as all the people you think of during the practice are mental objects. This bleeds out into your moment to moment awareness more globally, as well as your perceptions of the world, so often conditioned by fear and other barely perceptible traumas that more methodical, rational analysis are far too slow to uncover. Further to that end, Jim has an essay in Pearls of Wisdom called Rehabilitating Subconsciousness that I found extremely helpful, and your friend may too. I hope she's doing better now.
For anyone interested, here's a paper in which researchers applied Buddhist loving-kindness meditation to treat schizophrenia, whose cluster of symptoms frequently include depersonalisation. Researchers found the practice to greatly reduce baseline symptoms in patients.
ocrates.berkeley.edu/~akring/JCP%20Johnson.et.al.2009.pdf