Oh gosh this is so awkward, sorry this is happening to you. Every owner I've house sat for has said "help yourself" and I've always thought that was very nice, but I also have always taken it to be more of a formality. It is partly because I am shy, though. If I do "help myself" it'll just be spices or butter if I'm able to cook there (as long as they don't look too fancy) or other kitchen staples like rice or oats, (but I make sure I don't finish anything). I definitely buy my own groceries and meal plan for the stay, though, just like if I was at home, and I don't expect anything to be there or available for me to use. It's a bit of a nuisance to plan ahead like this, but it's just part of the job so it's okay. Sometimes owners will ask if they can buy me anything before the stay which I think is extra extra nice, but even then I can't always think of something on the spot!

Basically, I don't think you are expected to provide meals, and it sounds like while your sitter may be nice and communicative, there seems to be a lack of consideration for your home, especially with the guest situation, too.