Hi there dqah,
Welcome to the forum and thanks for posting here. It sounds like you have been super supportive to your mum which is so great but after so many years you must be exhausted from the worry you have for her. I can't comment if you mum is delusional but her pattern of thinking sounds concerning.
When parents are going through health issues, it is sometimes quite hard to direct them to get some help, especially as their child. I know this from my own experience with my mum. A gentle, or least restrictive approach is best (if possible) to protect the relationship you have with her.
Starting with a visit to her GP would be a good (and more gentle) first step. You might be able to convince your mum that she needs a visit to make sure she is going okay physically due to all of her experiences. You could ask to be present at the appointment with her. You might try to get a double appointment with the GP so you are not rushed. Going in from this angle might help a health professional understand some of the worries you have in regards to her mental state first hand.
If she refuses to go to a GP, you might contact your local mental health support line and get some advise specifically on how to get your mum's mental health assessed. Sometimes mental health support services will send out a team to your home if required.
If you are concerned about your mum safety, don't hesitate to ring a mental health support line like Lifeline 131114 or even bring her to the local emergency or 000. Sometimes if people are confused or paranoid, they can do unsafe behaviours. When people get paranoid in their thinking, it could be for all sorts of reasons, and getting a health check is important.
This is a really touch situation to be in and I hope you find some time to post here again on how your are going. Talking (writing) about it your circumstance can help immensely and there are a lot of supportive people here who have gone through a similar experience.
Sending you strength,
Nurse Jenn