According to the information you gave, I will try my best to help you analyze her situation and let you know her better.
1. According to the information you gave, I can see that she is a stubborn person. Such people have a strong insistence on their own ideas. So if your opinion is different from hers, she won't accept it. You can talk to her when you are free (QQ, mobile phone, etc. ), but don't go against her wishes. Whatever she says follows her, even if you don't agree with her, don't give the opposite opinion (even if you think her opinion is ridiculous). Because even if you did, she wouldn't listen, so why argue with her?
2, usually talk on the phone or QQ, she never tells you these worries! It can be seen that she has a strong psychological defense, which may be caused by successive blows. So don't try to enter her inner world at ordinary times, which requires high language ability and experience, and you don't. Once your intention is discovered by her, her psychological defense mechanism will automatically isolate you from her inner world. At that time, I was afraid I couldn't even be friends. That time she confided to you, it should be that you just met her, but there won't be many such opportunities.
Because she hides her heart, she should be lonely. So, although she says she hates you, maybe you are the only one who walks into her heart. So talk to her as much as possible. Remember, never mention her sensitive topic, that is, her inner world. It is impossible to try to persuade her. What you can do is to chat with her and relieve her inner loneliness and pain.
She said she knew everything. I think it's true. I believe that after so long, she should have figured it out a lot. However, people's psychology is very strange, which does not mean that they can certainly do it. Maybe she can see everything when she talks to you during the day, but at night, or when life is no longer satisfactory, she is afraid that she will not be so calm. So what she needs most is not your advice, but your support.
Give her a little more sense of your existence at ordinary times, that is, let her feel your existence and your support. This kind of support is silent and needs no superfluous words.
I can feel that she is a pretty strong girl. Have more confidence in her and hope she can get out of the shadows.