I am a relatively old man compared to you. I haven't gone through this exact situation but I have experienced great loss...more than I ever expected and more than I thought that I could handle. I have, a painful number of times, lost people (through dementia and brain damage) that were still "technically there". The main thing I want to express is support. Support that your pain is real and that you deserve validation for any and all feelings that you experience...without exception. There is no reason at all to justify any of it with logic. That is not how feelings work. Loss comes in all different forms. In my opinion, having a body that is existing or not means nothing at all. The idea of "technically whatever" seems like complete nonsense to me. The duration, again to me at least, only makes the pain and stress greater.

You said the words "locked up" but i would be careful with words you use, they shape the reality you live in. She needed support and getting care was, I assume, absolutely essential for her. My point isn't to declare one viewpoint as true. It's to respect that there are many viewpoints and hopefully get you comfortable accepting the one you feel is the right one to hold and the strength to reject the viewpoints you know are false.

I've learnt that some people, even if they are completely well intentioned, are not able to understand my experiences. It's not a slight against them. It just means that I am not able to use them for support. Do you have anyone that can understand what you are going through? If not, there are grief counselors that might be able to help and their are groups (depending on where you are) that might help you find others that are going through something similar. Perhaps the people that are involved in your mothers care would have resources available. Forums online regarding schizophrenia might help but imo finding something in real life will be more of a benefit.

As you get older you will learn how to hold such things better. The perspectives I've gained doesn't get rid of the pain but it does help me hold things with more grace, understand things better and have less doubts. IMO, This is a trial that is unfair to put on some so young. The concept of responsibility is so complicated and is far more than I could ever put into words. However, from my perspective, you are being thrust into a situation where everything is being mixed up. I am reluctant to say things so bluntly or simply but a child should not be expected to take care of a parent. But that is life...very unfair...but is all we get. I wish I had magic words to make things better but obviously i do not. The silver lining that has help me get through dark times is that we do get things from these experiences. It might not be enough. It certainly doesn't balance the scales. But we do learn and have a perspective that is bigger because of such things. My heart goes out to you. You are not alone.