The things is this girl is easy to handle because you have so much higher value and you bring a lot to the table. That is one of the reason this girl have let you so close to her. You have better health and more money, maybe even better looks. Girls are attracted to guys who have higher value. In this case you have many things better than her. You could settle and stay with her forever and it would be easy for you to keep her around and she would never break up with you. On the other hand you could look for girl who is a better match for you, someone your friends and family would accept more.
I agree you have to get it out of your chest to her. Say what you want from her. If she loves you she should have that energy to change her life. This is not a life shes living and shes far too young to give up on herself. Its not about you she have to fight for herself. Depression is a battle but so are life. This topic might help you to understand her illness.
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