DBT really is great for people who haven't learned to understand, accept, and appropriately express emotions. There seems to be a significant lack of providers who are trained in it, but that doesn't have to stop people from getting some benefit from it. If there isn't a therapist in the area who offers DBT, what's stopping you from learning about it? Maybe her therapist would be willing to learn, too. It might not be ideal, but would be better than nothing. You could check at behavioraltech.org and see if there are either DBT providers in your area or trainings that you would consider attending. Marsha Linehan's books and videos are good, and there are also some useful self-help books, such as "The Dialectical Behavior Therapy Skills Workbook" and basic summaries of the skills available online - see
http://www.dbtselfhelp.com/
I am a master's level therapist, and have not yet been able to go to trainings and get the certification I would like to in DBT, but I run DBT groups (I read both of Marsha Linehan's books and learned along with my clients) for youth in residential treatment. These kids often deny that they even have emotions, let alone words to describe them. They go from under-expressive to acting out of control, with very little in between. Those that are willing to do the work find DBT skills useful.
I also relate to alexithymia myself. Several years back, when I started therapy, I had no idea what my emotions were. I wrote an autobiography and my therapist went through it and labled my emotions for me. That was a start, and might be helpful to your client. What are her primary complaints? Can you give her some of the words to describe emotions associated with her symptoms, and check it out with her to see if it feels like a fit?
If you or your client are interested in knowing more about the effects of emotional abuse and invalidating environments, here is a link to one of my blog entries summarizing Marsha Linehan on that topic.
http://rapunzel.psychcentral.net/2008/04/14/lets-talk-about-invalidating-environments-shall-we/ Dr. Linehan knows what she's talking about.