My dog ignores my recall?

My dog is generally very good and sweet, I walk her off leash in the park (only the park) and I have no qualms that she will run off, she always stays in sight. But she won't recall, I have tried using treats at random intervals, and tried praise at random intervals. I use a happy cheery voice for the first recall and if she doesn't come in 10seconds, I use a lower sterner voice. This usually works but when other people or dogs are involved, I can't get her attention at all. She has this fascination of greeting and expecting attention from everyone. If someone so much as pets her once on the head or even say anything to her for that matter, I swear she would follow them home! This almost happened once where she followed a woman out the park, luckily the woman walked back to me but I need to iron this out. Since being off the lead in the park an hour a day she has been a wonderful dog at home, no house soiling, no separation anxiety, she's generally happier and amazing so I want to avoid taking the park away from her at all costs. She was awful before the park walks and use to tear up the house. When I recall at home and use commands she is extremely obedient and obeys straight away. But a puddle or a bug, or a nice smelling tree for that matter in the park and that's it I'm ignored. I've heard that I'm meant to call her once in a stern voice an if I get no response I quietly walk upto her and leash her for awhile or take her Home. I've tried this, but she explores too fast for an average human being to catch up with her. It's impossible for me to do that, I can't get her. Should I just keep following until I can get her n leash her? If this takes 20mins tho, she won't associate the fact she's being leash to ignoring my recall. Like I said, I don't feel Insecure that she will run off completely, but as soon as something interests her, I can't get her attention and it's driving me insane. She is a malamute btw, 3years old. What other ways can I get her to understand that when I say 'here' I mean business. One last thing, I have never called her for punishment, only good things.