It's much easier said than done, but perhaps you should be putting more energy into your relationship with yourself too, not just with her. Sometimes these issues arise as a side effect of the people in the relationship not taking good care of themselves and their life. Imagine getting yourself to a place where you feel confident again and secure despite whatever might happen between you two. Working on that magnetism created by self-fulfillment and self-focus might invite your gf to feel freer and more inspired to start pursuing and desiring you again. I don't mean play games, but just create a bit of space to recreate some of the desire.
Keep in mind it might not be in your control if it doesn't have anything to do with you. Your gf might be struggling with hormones, body image issues, stress, depression. Sometimes you get used to being in a relationship and take it for granted a little too (especially if she feels like the option is always there). If you pull back from always being open to sex, create a bit of scarcity, and show focus on your own happiness and your own life outside her, it might help her to feel less stressed and find her way back to you. It's understandable to feel unstable about things and it sucks that it sounds like she isn't working on things together with you, but maybe she's just not there yet. Give it a little time and trust that you're doing as much as you realistically can for the relationship.
Surprised I haven't seen this, but have you tried a different cable? Display port? Could be worth a shot.