Mentally ill grandmother who is paranoid, any advice?

My grandfather passed away and he always handled everything with my grandmother. Well, she is mentally ill, has borderline personality disorder, and likely paranoia. She goes to a behavioral center for meds and has a psychiatrist. She has been living on her own with help from her daughter and granddaughter. She lives by her daughter now but she’s super paranoid all the time and always lying and accusing people of stealing from her which isn’t true. She been accusing people of stealing from her for years (even when she lived with my grandpa). My grandpa always redirected her and he is the only one she listened too. Now she thinks the whole family is out to get her and tries to get strangers online or “friends” to pick her up and take her places. She’s secretive and has alternate motives. No matter how many times we try to redirect her and reassure her she’s okay and no one is stealing from her, etc., it’s like a viscous cycle. She literally bought a car behind our backs and wrecked it (she hasn’t driven in 15 years) thankfully no one was hurt. After we told her she doesn’t need a vehicle and we’d take her places, she then burnt down my grandpa and her house a week later. She was strong insistent on living there by herself before this happened. Again, thankfully no one was hurt. I don’t know what to do from this point. We finally got her beside her daughter in a safe house. Now she’s still night and day with her mood swings and way of thinking. She’s constantly plotting things such as leaving or accusing people of stealing. It’s too much. Need suggestions on the next steps to take.