She sounds vile.
I was baffled by your continued inaction and extreme passivity in all this. I was going to focus purely on trying to explain to you why this passivity has been working against you, and that you need to snap out of it and start working for your own side! Don’t be the classic: passive...passive...passive... aggressive Bite...then back to passive... passive...passive.
You aren’t setting your boundaries this way, and you are letting this awful situation continue because you are sitting there in silence not even registering even a tiny squeak of a push back so to an onlooker you might even be happy with the interaction. Which would be totally wrong and very upsetting for you, so you need to actually say something, politely is fine, but say something nonetheless! Bring your outside in line with your insides, and you’ll find this kind of situation much easier to close down much sooner.
Anyway! That’s all I’m going to say on the subject, because actually I’ve just caught on that it could be because of your confusion about her intentions - is she supportive or malicious?
At first glance it seems incredible that you’re still unsure after all this time and ‘action’. But the more details you let slip about the way this woman has behaved, the odder it sounds. Going through bins?!
And how very odd of her to try and talk about diets / weight / food just an hour or so after your little explosion which was Very Clear about your feelings on this.
Yet she can’t seem to help herself. And smiling all the time... it’s very, very, odd behaviour.
No wonder you couldn’t work out what on earth she was doing.
And in those circumstances, has it been this confusion that has got you so frozen and not wanting to act for so long perhaps?
I think her behaviour is explained by so many posters on here who say that she sounds like she has an eating disorder herself. Or she has some kind of psychological trigger situation happening around you, fixating on you and controlling your food intake in order to feel control in her own life etc.
That’s not to excuse her behaviour at all, by the way. There are many people with eating disorders who don’t feel the need to bully colleagues about food, and she needs to STOP. It’s simply a reason, an explanation for such odd and extreme behaviour.
I think you need to email your manager and get a meeting set up ASAP to discuss this situation. It’s not acceptable and now you’ve finally got it out in the open that you are feeling harassed by her, please get it stopped.