Dealing with paranoid delusions?

It's been several years since I've been on this forum (my dad who had Alz passed away in 2018), but now I'm back again since my brother-in-laws mother has dementia and it's been extremely difficult to handle.

My sister and her husband have been working on getting her meds on track, but until then we need some advice on her paranoia. She's extremely anxious and constantly skews every situation negatively.

There's a program in their city that has a volunteer senior 'hang out' with the patient so they can socialize and spend some time outside. My BIL told his mother that someone was coming to run some errands with her, and she managed to turn it into 'he's kicking me out of the house', she got extremely upset, started crying, and started to put all her clothes in garbage bags. It's been two days and she still believes he's trying to kick her out to the streets. He had to cancel the volunteer coming over.

She used to love painting, so they got her some small canvases, paint brushes, and paint in hopes it'll be therapeutic for her. When she finished the first painting, she said 'a man' wanted to buy her painting and it needed to be perfect, and she became very anxious, constantly fixing up the painting. My mom saw her painting and said it was beautiful. But that made the situation worse because now she thinks my mom also wants to buy the painting and she became so stressed on who to sell the painting to that she stabbed the canvas with a paintbrush and threw it. They have now hidden the painting supplies.

Everything I find on Google just says to talk calmly to her and try to gently change the subject but she will not be deterred. Also most of the advice seems to be centered around the delusion of theft.

Has anyone experienced this? Any advice? I appreciate everyone's time for reading this <3