This looks like it's an on line support group, but there is also a map with markers for what looks like local organizations, possibly in this area. By joining you might be able to inquire with others that have a bpd person in their family about DC metro options.
http://bpdfamily.com/
Also, you might look into Pat Harvey on this link. I think it's more training for families than an actual support group and costs dollars, but it wouldn't hurt to call her.
http://www.metrodbt.com/