My mom gets mad over stupid stuff?

Im 26 yrs old and I have had to move back in with my mom due to a roomate not paying her half of the rent. My mom and I have always butted heads ever since I can remember. Nothing is ever right or good enough for my mom. Her house HAS to be a certain way, if I leave my phone on the couch she picks it up and puts it on the table and says thats not where it goes...If I leave my car keys on the kitchen counter she gets pissed off yells at me and tells me why can't you put them in the right place they don't belong on the counter. If I have shoes in the living room I get yelled at, If its been awhile since Ive done my laundry I get yelled at. This is just the tip of the ice burg. When my Dad was here she was always yelling at him about EVERYTHING & ANYTHING. She has anger issues as well. If her computer doesn't do what she wants it to even though she's doing it right she flips out curses at it yells at it kicks it etc. If no one eats her dinner at dinner time she throws it away and goes on a tangent. She goes to the bar every day and when she comes home as soon as she walks in the door she'll ask me questions like have you fed your dogs even though its 2 hours early, have you watered your plants? have you done this have you done that day in and day out. IF I say no I get yelled at WELL WHY NOT. If I put a dish in the wrong place in the dishwasher I get yelled at and reminded the "right" way to do it. If I sleep in till 10am I get yelled at. We are paying her rent (even though the house is in my name after my father passed ) its still her house since it was hers before mine. I asked her would you treat a roomate this way mom? and she said yes. Right now I told her my husband was not eating and I hear her slamming and banging stuff in the kitchen getting even more mad. SHE DOES NOT ACT LIKE THIS WITH HER NEW BF SHE IS SWEET AS PIE. She is SO different around people she barely knows and I dont think anyone but myself, my husband and my father know how she really is. Its making it nearly impossible to even want to be close to her anymore and I don't know what to do. I wake up with tension headaches, I have so many gray hairs its unbelievable and I believe my mom could be the reason I have so many damn mental problems. WTF is up with my mother? Oh and might I add she's not my real mom she is my grandma but she has raised me since I was 6 months old and she isn't my biological grandmother but none the less she is still my mother. She's been to her general dr that put her on some anti depressants that she stopped taking once she started meeting people again. She's 78 yrs old and I dont think she'll ever be out of her ways. Shes not the typical 78 yr old either shes fiesty as all heck. I can't handle this anymore. This is the reason I ran and I ran fast the first time I left home. WHAT IS WRONG WITH HER?!?!?!