Narc parent & dealing with them

My mum is a text book narc. Loads of childhood trauma, she passed on as a young mum to her children. My dad is a flying monkey/ enables the bevaiour sadly. We always say if she murdered someone, he would just grab a shovel & join her. Married for 57 years, nothing is going to change. Now they are both 80 years old. I rasied my 2 girls as a solo mum for the past 12 years. It was hard, my mum distanced herself as much as she could from assisting me with child care. Very full of herself, self absorbed personalty. Now my girls are 25 years old & 23 years old. There dad died 3 years ago. He had a mid life crisis about 12 years ago & left the family for a gold digging woman he met at the local casino & sadly was not a positive influence on him at all. She had her own agenda with little care for the well being of his 2 teenage daughters. I always say to friends, my mum is my biggest critic. She is nasty with her words, hurtful & my sister has had nothing to do with my parents for over 10 years due to mums behaviour. My question is how the heck do middle age woman survive & thrive in life when you have a narcissitic mother?? Any chance she gets, she will throw me under a bus with my 2 girls, she thrives on gossip & most of her life conducts herself like a spoilt, needy15 year old teenage girl. Now that she is aging, she is jealous & down right nasty towards me. I make food & deliver to her, rather then a thanks she tells me how the food at the local pool is so good. I remind her, it costs money & not home delivered! She is most of the time, ungrateful & always trying to one up me, very competitive & sees everything I do, as something she then has to do, bigger & better then I can. I am not competitive at all. Very humble personalty, but it is hell having her as a mum.