Was going to say you're in the wrong, but read through the comments first and now I'm confused.
On one hand: partners should support each other, within reasonable limits. Her parents might not be "helping" her as much as you think. She's not asking you to take her out for fancy meals every night, she's scrounging through old leftovers. This tells me she actually is going hungry. And I honestly cannot imagine eating in front of my partner knowing they were hungry.
But after reading the comments, I understand that you feel like you don't have the opportunity to eat without her there, and that you're not inviting her over.
This is a conversation you need to have delicately and thoughtfully, while no one is starving. I'd encourage you to make dinner together tomorrow night (I'll post a great and super cheap recipe below) and then have a serious conversation. What's really going on with food, with her, with her parents? How are you guys going to address this?
Best cheap lentil soup
-dry red lentils (you can get a bag for a dollar or two)
-wash lentils until the water runs clear (this will take a couple minutes, longer than you think)
-simmer the lentils for half an hour
-if possible, crush garlic, mix it with salt, pepper, coriander, fry it in olive oil for a minute, and then add it to the soup. you can also skip this and just add chopped or crushed garlic to the soup while it's simmering. just make sure you add plenty of salt to the pot
-squeeze lemon juice on top before serving, add black pepper or cilantro on top if you want to be fancy
It's pretty much this recipe - https://herbivoracious.com/2008/04/recipe-syrian-y.html
The great thing is that it's really hard to mess up. It can be as thick or thin as you want.
Let us know how it goes. You don't say how serious this relationship is. You don't need to stay with her out of obligation. But if you're thinking of splitting, do it kindly, and help connect her with whatever resources she needs to get through this.