My nana is convinced she is in a relationship with Elon Musk & spending all her money. What do i do?

My (22F) grandmother (74) is convinced she is in a relationship with Elon Musk and is losing thousands, and putting herself in danger. About two years ago, my Nana started showing signs of being, senile? I dont wanna say dementia because she isnt diagnosed but my mom thinks it could be onset. In 2023, My mom, her Fiance, and my little sister (15), moved in with my nana whos been living alone since my papa passed in 2019. My nana has never been naive, but two years ago she started talking to who she thinks is Elon Musk, who is obviously some scammer guy from another country, who she literally sends thousands of dollars to in gift cards. When i first heard about this, my mom wasnt too worried because she was first able to explain to her that she was being scammed. And she seemed to understand. So i thought it had passed over, because it was never brought up again. We stay in touch as much as we can, since she lives a few towns over. When i do see her, she is always in good health and mind, and is always her bubbly sweet self, that shes been all my life. Well sometime after that, i guess he was somehow able to convince her he is real and in love with her. The “billionaire”, needs money, and she sends him gift cards all the time. I cant say an exact amount she has sent, but its enough to make her bank suspicious enough to know she was being scammed and cut her off, to which she would just switch banks. He has also sent grocery’s to the house, to i guess convince her he is real and not AI, meaning she has given him the address to the house my mom, and little sister also live at. She has sent him photos of all of her grandkids, including me, and trusts this guy more than her own family. She has completely cut off my Aunt & Uncle, her kids, because they keep telling her that it is a scam. She has almost kicked my mom out for the sane thing so my mom just started to kinda stay out of it. I didnt know it had become so extreme until today, when she had texted me,
“I am getting married Nov 15th in Florida at mine and Elon’s house. He built me a home in Austin earlier this year!”
Which really concerned me so i called my mom right away and asked her what was going on with Nana, and she told me everything ive basically said, and more. Like how my nana wants to get a boob job, and face lift. Which she hasnt found a plastic surgeon crazy enough to do it for her (thank goodness). She has always been against things like that, always told me growing up natural was better, and never even wanted a tattoo, and wasnt a fan of my moms or mine. But is now wanting to get plastic surgery! Well i guess she has almost lost all her money, even though “Elon Musk” is a fucking billionaire, she is still convinced that she is going to get married to him on Nov 15th in Florida. She has even started to lose her memory in a weird way. Like saying she has actually known Elon Musk and been in love with him for 15 years now, which she was married to my Papa then, and until he died. She also tells my mom that she went to Texas and was drugged and kidnapped, and then came back home, all in the matter of one day. We live in the PNW, so that isnt possible. My mom doesnt know what to do, because my nana is still able to take care of herself, so she cant just take her cards away, or her phone. And is afraid the police wont do anything because she technically is of sound mind enough to take care of herself. My mom said she did get ahold of my nanas phone one night and seen that she sends all these photos to him of all of us, and sending him $500 gift cards at times. Which, my nana doesnt have money like that and im afraid she could be completely out of money by now or sometime soon. Im not sure what to do. I dont see how the police could do anything about this scammer in another country. Not even the bank can convince her she isnt in a relationship with Elon Musk, so how could a cop? Since I just found out about how bad this actually gotten, ive decided to kinda take the approach of, telling her im happy for her and that i would love to go to this “wedding” in Florida, all the way across the country. Because im hoping i can find a way to stop all this and show her that this guy is lying to her and scamming her. I dont want her to get hurt. More than anything i am worried about her safety, and my familys. Especially since she is talking about taking my little sister to this wedding, on a plane. Which my mom has forbidden, but its still scary to think this guy has our address, and has completely gotten her trust and she is choosing him over her family. I dont want her to cut me off so im trying to act supportive, hoping someone might know a way i can deal with this. Or if this sounds like she is possibly getting dementia or something, and if so how i can help her realize the truth. Thanks for listening.