Obviously, I would be inclined to agree with AD21. I note that, although iatrogenic memories are possible, they are not the norm. Concern, does your mother have a therapist that she is actively working with? If so, it may be time to schedule an appointment with that therapist to discuss the complex changes that may occur when your father deploys and her world destabilizes a bit. That may also give you an opportunity to discuss your concerns and fears. The therapist may well, without breaking client/therapist privilege, be able to provide you with cogent support and commentary that will help you formulate a dir4ection.
I too suggest speaking with your mother, talking with her about how she perceives her needs. Sometimes significant change galvanizes an internal community into greater coalesced activity and internal communication with less conflict and tension.
I note the shift of diagnosis from MPD to DID is insignificant, but simply reflects the change of medical nomenclature. From the information you provide, it would seem that your mother is a non-coconscious multiple, meaning that at least some of her alters are unaware of thoughts and feelings sustained by other alters.
Important in all of this is to set your own boundaries. You cannot afford to focus completely on your mother's needs; this is not healthy for you or, frankly, for her. As you develop an understanding of her behaviors, be clear about what you can handle and what you cannot, always being mindful of gentle language. However, it is possible to convey, in a caring fashion, your need for personal time and interpersonal boundaries.
If your mother is not in active therapy with a skilled trauma therapist, your best commitment to her will be to seek to get her to establish such a liaison. A trauma therapist, skilled in understanding dissociative competencies can support her in ways that you, as a layperson, cannot and should not. In addition, if you can support your mother in developing internal communication skills, such as journaling or art therapy, this may help to extend and amplify the work of a skilled therapist.
AD21 cites some excellent resources that may provide you with more information and, thus, understanding.
Discuss