I completely empathise with both of your points of view, but I can only speak from my own personal experience. I spent 8 years of my life in a relationship with a guy who had mental health issues, he had the same concerns as you, he didn't want to say 100% yes or no about having kids in the future as he couldn't in that moment see himself having them due to his issues. He would say to me "how can I look after a child when I can barely look after myself" which is a completely valid point. However, I made it very clear early on that marriage and kids is a HUGE thing for me, and I did not want to waste my time with someone who did not want the same thing because what's the point? To placate me he would say let's just see what happens in the next year... for 8 years. I didn't want to leave him because I loved him, but finally I had enough. I had spent almost a decade of my life waiting on him and he clearly did not want the same thing as me. When we broke up he was relieved I think and admitted to me deep down he knew he never wants to have them he just didn't want to lose me because of it. Within literally months of leaving him I met the love of my life, we have a beautiful son and we will be getting married next year.
As much as you might not want to, you need to sit yourself down and have a serious think about your situation. Your partner has already spent 4 of her prime years waiting to see if you are the one willing to be her partner in raising a family, do not be like my ex and make her waste another 4 years because you can't be honest with yourself. There is absolutely nothing wrong with you not wanting children, it is your life and your choice. While you may have other things you'd rather be working on with your mental health, this needs to be a priority. It is a fundamental aspect to your relationship, maybe not for you, but certainly for your partner who is 100% clear where she stands on this issue. For her sake, you need to be realistic on if its ever going to happen, and if its not then you need to let her go so she can find happiness with someone who wants the same as her. Best of luck to you OP, I wish you both peace and happiness ❤