Shih Tzu leash issue

Hello! I have a lovely little shih tzu who is 6 years old. She walks beautifully on-leash in our neighborhood and on roads in general (it is rural and quiet). However, whenever we go somewhere with lots of people, she gets so excited that she pulls and pulls on the leash until she chokes herself, and starts hacking. I know most of this problem is just exposure to different situations, but the issue my family is having is that we cannot correct her without risking injury (trachea, etc). If I walk her alone and she veers off path, I can tug gently at the leash once, and she will return. But we can't do that when she's pulling and trying to gallop to her favorite thing: people.

Any suggestions? I do think returning to a front-lead harness would be a good idea (she used one as a puppy in training), but other than that I've no clue. Thanks!