I have a slightly different perspective to Amanda Louise and you can take from this what you will.
I have DID and my T and I use IFS as our main tool. It most definitely can be used in people with dissociative disorders as well as people without them. I think of it like a massive spectrum from normal and integrated parts of self that everyone has all the way up to fully dissociated parts of self that can be called dissociative alters. There's that massive continuum from completely normal to DID. OSDD type alters (DDNOS) fall on that spectrum too.
When a young child is traumatised the developmentally normal process of integrating the various parts of self into one sense of "I" can be disrupted, causing varying levels of dissociation between the normal parts of self. The greater the trauma the greater the disruption and the greater the disruption the greater the dissociation between the normal parts of self. When the disruption to normal integration processes is extreme it can result in fully dissociated and amnestic self states or alters, that is DID.

I say this to point out that you can not be a fraud in regards to this. The self states are normal. Every single person has self states (even though everyone has varying degrees of defenses or dissociation bertween them). The defenses and degree of dissociation between the self states are the parts to work with. It doesn't really matter if the self states are fully dissociated partially dissociated or whatever. Using IFS you can work with them just the same without needing to worry about labelling them.
In IFS clinicians amplify the separation between parts as part of the therapy. That is not going to cause greater dissociation or anything like that. It is in service of creating greater self-understanding, which leads to greater compassion, acceptance and integration of the self states.
Anyway, it doesn't matter where on the spectrum of dissociation your self states fall. Although I have the "label" of DID it doesn't matter much in IFS therapy. We have to adapt IFS techniques at times, but it all works out. The beauty of working with IFS is that you can forget about the diagnostic label and just work with whatever the parts of self need, without needed to label them as anything. You can just work with them as they are, and with whatever they need.