Melbourne

The only physical effect I can think of that might be relevant is that sticking to such an extreme diet occupies all available brainspace, leaving no room for anxiety. But you'd pay a heavy price for not doing anything other than watch your diet and stress out over whether something was or was not keto. As with any extreme diet, you really have to make sure you're getting all your dietary needs met, and extreme diets really really limit your options. And they all have a built-in guilt for failure stress included.

I have a feeling that taking this option really isn't wise, but you do you. If you wanted to try it for a while to see if it helped, well why not. But I also wouldn't beat myself up if it turned out not to be helpful.

And then you can say to aunt, well I tried it and it didn't work for me. Which might shut her up.

I think her controlling your diet will make her feel less anxious.

I've personally been on keto on multiple occasions and definitely noticed improved mental health, including reducing anxiety.
I feel like it's the best diet for me but it's hard to keep it up, most of my social events revolve around meals and alcohol and it's just annoying and tricky to stay in keto - and it's really an all or nothing kind of diet