Oh my Lilo was the most stubborn puppy ever when it comes to walking on the leash so I can relate. lol She's still difficult even at 8 months old, but much much better than she used to be. Just keep at it, use treats as bait to encourage her to walk (in my experience, they have to be really enticing treats like pieces of meat or cheese, whatever your chi goes crazy for) and praise her a lot when she does walk. Also have you tried leaving the harness and leash on in the house so she can get used to it? I think with time and patience, she'll get there.
My previous chi Coco was resistant to walking on the leash too at that age, but she warmed up to it after a while and ended up crazy about walks.