My mom has gone from sweet to "Hell on Wheels" in 2 days. Any suggestions?

My mom is on Alzheimer's medication she's 79 and lives at home with my dad. I go over every day when I get off work and every weekend. She doesn't cook anymore, clean, doesn't know how to do her hair, but she's been pleasant and remembered things pretty good until today. Today she was vulgar, mean and just angry so when I left to go home within 20 minutes my dad called and she tried to stab him with a fingernail file the old-fashioned metal ones that kind of a point- he got it from her and she went in her room and slam the door. I sent my son over and she was calm and happy to see him so then I called she answered the phone she sounded happy. I said hi Mom, she slammed the phone down so I called back and dad answered and then I hear her in the background her telling him to hang the phone up and not to talk to me. This is very hard but I'm more worried about my father. I told him to lock his bedroom door at night but he said that he wouldn't hear her because they always slept in separate rooms. I don't know what to do.