I have one w/this same problem...Momo ate a queen palm fruit w/seed when he was 7 months old & it caused a blockage. Had to have surgery to remove it. I've considered muzzles, but I learned in grooming school that it should only be on the dog for a very short period of time. They can't breathe very well w/ it on, esp it they get hot or worked up (which they do bc they're not used to having this weird thing covering their snout), so it's def not recommended for walks. I've also considered gentle leaders, but couldn't find the right size for a 5# dog.
Since then, I taught all my guys the commands, 'drop it' & 'leave it'. You can search vids on youtube, I learned from watching Victoria Stilwell's show 'It's Me or the Dog', she uses the take it & drop it cues.
Another thing, maybe you should also consider cutting all treats (unless it's for training) so she gets hungry & set a routine meal time. If she doesn't eat, take away her food bowl after 20 mins, then give it to her @ her next meal time. Hopefully she'll eat bc she's hungry. Ideally, it would be best to eat b4 walking, but I have 1 that refuses to eat & will eat after her walk loll! Best of luck to you & Izzy.