DEAR HARRIETTE: My friend is on some sort of weight-loss kick and is now trying to convince me that I need to follow her new routine as well. The diet that she is on is too restrictive for me. I have had a long, complicated relationship with yo-yo dieting since my teens, and I am just now starting to fix these issues — well into my adulthood. My friend is naturally pushy, but I don't think she und…