Half my front tooth is decaying and mom doesn't care?

I've had really bad teeth all my life and back in 2015 I noticed a cavity on my right front tooth gumline. It didn't seem like a threat since it was SO tiny, so I just ignored it. Now however, it's taken up half of my front tooth, the embarrassment of going out and smiling and even talking is horrible. Every time I open my mouth the first thing you'd notice is a HUGE brownish/yellow part of my tooth. I told my mom about it and it's progress and all she had to say was "You did this to yourself so don't bother me. It's your problem". So apparently going to a dentist is out of the ball park since she's being completely unsupportive. I'm 17. No, job. No money. And I'm pretty sure my insurance doesn't cover anything dental (According to my mom). So what can I do outside of brushing and flossing to save this tooth? I'm on the verge of completely giving up and letting it just rot away. If I can't have any professional help, what IS there to do? Sometimes I just want to knock a brick upside my mothers head due to her own arrogance. When it's not her problem, she doesn't care or she stalls to focus on it. I had an abscessed tooth once and my face was swollen and I begged her to take me to the hospital, she refused, so I had my sister take me and my sister and Mom got into an argument, yet when my mom felt the side of her face hurt one time, she immediately rushed to the hospital just to find out nothing was wrong. I'm completely helpless.