How do I stop my housemate from stealing my food?
So, I (29F) have lived with the same housemate (67F) for close to 5 years now, and I have had issues with her taking my food. Over the years, I have had countless conversations with her about it and tried putting systems in place to limit her taking my food. I separated the fridge so that my stuff would be on the left, and hers on the right. Despite this, she still kept taking things from the left (and still does to this day). So I started putting brightly coloured stickers on my things and told her anything with a sticker was mine—yet, she would still take it and say "Oh, I didn't see the sticker".
Next phase was physically writing my name on everything, which can be time-consuming. She would STILL take it and claim she didn't see my name... So, I started putting large white labels on everything with my name written in large font in texta. She still takes my food. Last thing I tried was asking her to label her own food (because why should I keep wasting my time for a system that does not work) and I told her to assume anything that DOES NOT have her name on it is not hers. Again, this made no difference. She still takes my food.
I don't know what more to try, because clearly separating or labeling things makes no difference. Confronting her about the subject does nothing. I find myself getting more and more frustrated and angry with her, but I internalise it.
It's not just the food, there's much more she does to upset me, but that's one thing I should be able to have more control over and I feel defeated. What can I do?