Coming to terms with what kind of person my mom is

So after discovering this sub I've realized that I've been dealing with a narcissistic mother for years now that's only getting worse. The event that made me feel off about her and changed how I thought about her was in high school when I was stressed out dealing with bullies and her response was to laugh at me and call me a "spineless jellyfish".

Later in college when trying to explain to her about my depression and social anxiety she scoffed it off, exclaiming that she never had depression when she was my age, and at 23 I was simply "too old to be depressed". She's retired now and I live with her helping around the house since she honestly isn't competent enough to do much (with live in a rural area and even after 6 years she can't figure out how to start a lawnmower herself) so I feel guilty if I left her alone, but lately not so much.

She has usually held a part time job despite being retired to help make ends and keep busy, but helping her out has enabled her to point where she believes she's beyond any sort of responsibility. I don't make much money but try to help her out financially when I can, but it's hard to sympathize when she sells her perfectly fine car for a brand new one...a week after she didn't have enough money to pay the electric bill.

I'm dealing with my own personal demons (and by dealing I mean bottling up and letting boil inside of me since I feel ashamed to go to therapy) and working a strenuous warehouse job doesn't help matters much. My mother will do anything but accept responsibility for her financial situation, spending all day watching TV and on Facebook. As much as I do for her whenever I don't have enough money to pay her bills she complains that I never want to help her out.

I'm raised in a single parent house so I barely talk to my dad. But my mom wants money so much that even at 26 she'll find any excuse to take my dad to court over child support. Child support that goes directly to her obviously since ever since I was 15 I've been responsible for my own bills and I hate asking for money. She has even lied in court about college courses I hadn't taken to attempt to squeeze more money out of my dad. Even other members from her side of the family keep their distance from her and admit there's something mentally wrong with her. I love my mom, but at the same time feel neglected and taken advantage of, and I just don't know if I can even get through to her since she usually dismisses anything I have to say.

Sorry for the long winded rant that wasn't structured the best, just had a lot on my mind.