Thanks so much for taking the time to send this through. I'm sorry that your parents are struggling with mental health and of course this is super worrying and hard for you too.
My parents both struggled with long term health issues when I was your age and my Dad had a severe mental health breakdown.
I remember feeling very anxious, helpless all the time, and completely alone in how to deal with them and my own emotions as I saw them repeatedly struggle.
One realisation I had to come to terms with was that ultimately I was not responsible for them. For as much as I cared and wanted to help, I had to accept that I wasn't the right or appropriate person to always help them and I had to leave it to those that were older and more skilled and professional in this area.
I want to encourage you Ella to wear the right level of responsibility with this. You can't fix this but what you can be responsible for is being a great daughter, helping in the small ways to help take pressure from your folks. You can be responsible for looking after you and continuing to make wise and good choices for your life. Try to find the right balance in worrying about this versus enjoying life.
So be careful of your environment, make sure you have time outside of home, for friends, hobbies and interests that will see you focused in other areas not just your parents and home life. This will help you a great deal to have safe life-giving external places and spaces, and it will also give you strength for home life too.
Be careful not to let the little voice in your head win that says if you do all of the above you don't care enough, or that you're selfish or your priorities are wrong. Those thoughts are not true. The very fact that you wrote to us shows that. You are important too and to help your parents you need to help yourself
As you said, you can't make them talk but you can talk to others.
Make sure you get help, reach out and talk to others. Don't be afraid to see your GP. Seek help from your school. If you have faith and go to a Church, seek help there too. There are so many that would want to support and help you through this and speaking as a Christian I know that God would want you to know that you are loved, supported and cared for too - just like your parents are also.
Cheering you on, and hoping this has been of some help and encouragement.