This is a classic mistake men make. As a man, I've made this mistake many times in the past before I learned what was happening. She's not wrong. You're solving for the wrong problem.
At least three times a week, she tells me she felt bad that her coworkers didn’t have a lunch,
She was sharing her thoughts and her feelings with you. She was creating a moment where you were both looking through her eyes at a situation of sorrow. That was her goal. You felt that moment and empathized with it. Ideally, you'd even communicate to her verbally how sad it was. That was the complete thing she wanted from beginning to end.
However, you misinterpreted what she was saying and why.
so I adjusted my cooking so her coworkers would have some sort of lunch if they didn’t or couldn’t bring anything.
You felt the empathy, but then you designed and implemented a process to solve the problem. THAT WAS NOT HER GOAL. I assume you told her the leftovers for 4 were there for her to take, but that wasn't what she wanted. She never wanted to take leftovers for her coworkers. Bringing leftovers can cause all kinds of other social difficulties she may not want to deal with. She wanted to experience the moment with you about how bad it was he coworkers didn't have food, perhaps even gain understanding about their social and economic situation of her coworkers, but that was all, not "FIX THE PROBLEM".
Stop bitching about coworkers not having enough to eat if you’re not going to fucking help.
The anger you're feeling telling her to not talk about a problem unless she expects a solution is the same level of anger she will feel when she expects you to listen to a problem and not offer a solution and you don't honor that.
A way to approach this in the future when she talks about how sad she is for her co-workers is to ask her what she'd like the out come of the conversation:
"Would like like me to simply listen, or are you looking for a solution?"
If she says "listen", then you job is to sit there, listen to her story, experience the anger/sadness/frustration she did/does, and simply acknowledge it.
- "Honey, I'm sorry. It shouldn't be that way"
- "That really sucks. I hope it gets better for them"
- "That must be hard for you so see that everyday"
There are piles of books on this, one of the most famous is "Men Are from Mars, Women Are from Venus". If you have any desire to have a future where you spend that with a woman, you need to understand differences in how each process emotions. If you simply say "it has to be my way, and a solution is the outcome when a problem arises" you will alienate your mate putting distance between you and possibly lose her.
I know its hard. I know its uncomfortable and frustrating for you. I've been there myself. I know "it would be so much simpler if...", but it isn't. This is what it is and you have a responsibility to change your behavior here too. You know when they say "a marriage takes work"? THIS is some of the work they're talking about. You've punched your time card for your morning shift and are now on the clock. Get to work.