Delusional jealousy and dementia; not sure what to do here given her refusal to see a provider.

I'm very new to this forum and community, but thought I would reach out for any help or shared experiences that anybody could offer since I'm pretty desperate for any guidance:

Background:

I live in California but my parents live near Seoul, Korea and have for some time. My dad is 70 and mother will turn 69 this March. I see them about once a year but keep in touch with them at least weekly via FaceTime.

About a year ago around February 2018, my mother started accusing my father of cheating with other women. No one specifically, but just generally. According to him, it started off with questions about where he was when out and about, then she started checking his cell for chat or call records. When my father denied he was seeing anyone and showed him the phone each time, she accused him of deleting the chat or call records along with heavy verbal abuse and yelling. It quickly came to the point where she was sleeping with his cell phone beside her for those incriminating texts or calls that of course never came. Nothing my father could offer ever seems to satisfy her that even though she has no evidence, just a bunch of unfalsifiable claims when the burden of proof of course is on her for such a serious accusation. She also said she was "missing" some personal items like makeup and such and is quick to accuse my father for "stealing" them and giving them away to these "other women".

When they came to visit me last October for a month, I saw my father's meticulous record keeping of this and everything he's had to live through to date and its clear she's under a delusion and not letting this go. He also managed to secretly record a handful of of the times she has an enraged episode and was also able to share it him and a local psychiatrist, who highly recommended she be evaluated. My dad pushed her to go with him but of course she refused and was insulted for being called crazy, when this delusion in her mind is firm and real.

Last month, she started demanding that he leave and start a divorce, and her reactions started to become violent (pinching hard enough to leave marks, striking, including a contusion on his lip) and made death threats. I personally listened to a disturbing recording of one these episodes that happened just earlier this last Monday, and was alarmed enough that I convinced him to leave for a local hotel as soon as possible that day. He's still currently holed up there and I'm videoconferencing for many hours with him everyday. The local psychiatrist also heard the recording and immediately advised separation since my father seems to be the stimulus and target of her episodes.

I've called my mother daily since and listened to her, and she seems lucid otherwise and doesn't seem to have obvious memory problems. She told me he just left to be with some other woman (though I know the real facts). After sharing some of the calls with my dad, we're in agreement that she's probably not a danger to herself. I made sure that not to challenge her delusions and try to make her feel not abandoned and alone. She's not aware that my father has been in heavy correspondence with me over recent months over her worsening reactions. I told her that I'd be flying over "asap" though gave no specific date yet. In reality, I will be flying out secretly this Tuesday to meet with my dad for a few days first before I head over to see mom.

Sorry for the long background, but is her type of delusion and reaction in line with what others might have experienced with respect to dementia behavior? She's not quite 69, but I think it could be a possibility. Just really not sure what to do here given her refusal to see a provider.

Any other symptoms I should be on the look out for when seeing her? She did mention she was having lots of trouble sleeping through the night in recent months.