You handled the situation well. You spoke with them and they didn't listen so of course you had to go to the landlord. At least she was understanding.

Also, just to interject, not all "bigger girls" want to eat all the time. That's kind of a stereotype, why did you need to tell us that she's bigger to point out her annoying behavior about food.
I'm fat and I took a little offense seeing as I know skinny people who eat way worse/more than me.

Other than that, I hope the situation clears up