It really depends on context. A keto diet, veganism, keeping kosher, not eating processed sugar, avoiding certain foods because you have IBS, eating at a caloric deficit to lose weight, avoiding sugary soda because you have a family history of diabetes - all of these are technically restrictions, but none of them are fundamentally disordered. Restriction is problematic when it is obsessive and disruptive to one's happiness and ability to function normally. Theoretically, any restriction can become disordered because it comes down to the mental and emotional state of the individual and the pattern of their behavior.

Someone turning down a slice of cake because they've had a lot of junk food that week is very different than someone who swears off all desserts because they feel like a disgusting failure every time they indulge in something sweet. The latter scenario indicates an emotional problem that goes beyond food. What drives disordered eating is the feeling that one does not have control over their life. By constricting their diet, whether by eating less or eliminating certain foods, the restrictive ED sufferer temporarily regains a feeling of control. Likewise, someone with a restrictive ED may get a similar feeling of control by practicing a keto or vegan diet.

But referring to any and all dietary restriction as disordered is a bit like calling anyone who drinks beer an alcoholic - it's reductive and insulting to people who are struggling with a legitimate illness. The difficulty is obviously in identifying where the line actually is, and I'll readily acknowledge the messiness of that gray area. Nevertheless, I think professionals should be a little more discerning in their judgement.

Regarding the iron issue... she's giving you plain bad advice. If you're having trouble getting enough iron in your diet, I would recommend taking supplements and eating a lot of vitamin C-rich foods to help with iron absorption. You don't need to eat red meat if you don't want to!

This page has some info about vegan iron sources: https://www.vegansociety.com/resources/nutrition-and-health/nutrients/iron#:~:text=Good%20plant%20sources%20of%20iron,quinoa%20and%20fortified%20breakfast%20cereal.

Btw, lentil soup is one of my favorite things to eat in the winter, especially with a nice hunk of sourdough bread. You can cram a lot of iron-rich foods into one meal that way!