Mom is 77 and something is wrong. I need advice.

Mom stated on my BD t hat she hates, wants me dead wants to kill me etc etc. I started trying t get her tested for alchzmers or dementia. i make an appt she refuses was always a reason. her behavior has gotten worse over the last year. last week i caught her putting her evening meds in my gall of kool aid. me stomach had swollen i was to the point i couldn't drive &was peeing brown. Yes when i caught her i yelled at her is freaked me out. next morning she gets up sits down gets back up after the coffee was boiling got a cup and threw it on me burning my chest, not badly but it was red. well i lost it again we went in the liv rm. i tried talking and she reached down in the side of her recliner and i thought she was going for her chefs knife... i jumped up restrained her. before i could get her strained she clawed my chest, punched me in the lung, & kicked me in my vagina. She had spent t he day explaining how it was ok my dad had slapped me down a table at 2 and her ex husband had molested me at 14 and she left me with him to fly to Denver,,, after all we do what we have to do to survive. etc etc. even reminded me how she would tie me to the bed. Things i never wanted my son to know abt her or me. He is mentally ill and i keep a lot abt my family hidden to him. I know this sounds crazy but i lived it all this last week and it was painful. So after that she jumps up says want to take a bath. which kinda shocked me.. so i followed her in there and she was trying to take a face down header into my tub and not use all the rails installed ard it. so i grab her again and she starts screaming to my son i was drowning her. i wasn't there wasnt but an inch of water int he tub. she sits there for a min and i go get her robe and panties hand them to her she dresses a nd says she cant snap up the robe. well i try to snap it and she is wiggling backwards and reaches up starts hitting herself int he eye screaming my sons name i was punching her he was there said no nana you are doing that finally i don't know how we all got out of there & she went to bed. next morn she says cat ate an 18in piece of plastic & left to go to vet. gets back a couple hours later says vet sending her to another town. we live in rural Okla. well at 1:45 i find out phone off the hook had my son check the phones and she has the one in her room off the hook. I call vet get inst. go out check her cars oil and etc because that place is at 1.5 hrs away and nothing between here & there. she throws the cat in the car and herself starts the car and it cant start i have the cap of teh oil to add oil and the dip sticks out. she jumps out runs 1/2 block away to the neighbor screaming elder abuse & call the sheriff. Well she comes back gets in her car drives back to the neighbor waits 2 hrs for the sheriff who talks to her comes over talks to me says yeah mom is changed something wrong call APS on Monday. in meantime she leaves he says she is getting a hotel in town & we have a nite off and leaves. 6AM i fond mom wondering my house the following morning seems she says the sheriff told her to sleep in my driveway... sighs. well i get the cat call the vet in a closer town get mom and my son into her car we drive there get the meds her cat needs and then over to another town to get her meds filled.. she was out well we get there send my son in with m CC and she leans over punchs me in the breast jumps outta the car and runs in there screaming elder abuse. Well the cop in that town was a complete jerk told me off the record i was a big ole girl and prolyl did t hat adn if anything else happens i was going to jail. refused to look at the burns, bruises and etc... cause she is old and i am a large fat woman i was in tears.felt liek i was in the movie deliverance. We get back home and guess what we drive up i go to my room and she calls the sheriff ...elder abuse again... well the neighbor calls APS and they get her.. since they got her last sat s he has been back to town talking to my neighbors in a town 40-50 people i am humiliated as i do not socialize with a lot here. she is now calling me wanting to come home crying and things.. but she has always been mean and manipulative and off the chart i thought people got old and calmed down not meaner. and i am scared of her and i am terrified i will loose my son over this or end up in jail because she is an excellent liar & actress. She is not frail she is acting. what do i do i am scared to death for her .. my son and myself. I am not a mean person i am just tired of all this and i can not take it anymore, she is destroying my life.