There's a thread in Significant Others from a non who is seeing someone who apparently has DID. Since it IS an SOFF thread (where Nons are allowed to even be critical of someone affected with a disorder) it could be possibly a little triggering, so consider this a trigger warning, although to me it is quite mild. With that caveat out of the way, if anyone wants to check it out and offer any advice, here's the link:
family-support/topic222062.html#p2304676