OK then....can't help you with the why but how about this: Work on luring her into fast, fun, on-leash u-turns.
FUN. Play, the best treats you can muster, a toy that turns her on, running, whatever gets her following you. Do this around the house, or randomly on walks when she's already following you, make it a game and give it a name.
Do this until she's pretty solid and reliable about it.
Then when she stops and plants, walk a few steps in the direction she wants to go in, then do the u-turn game.
Although I think there are times (depending on the dog) when it's fine to use negative/punitive measures, it's not fair to make the dog scared or mistrustful, and it seems Daisy might react this way. That's assuming she really is, and you are not being overly-solicitous of her behaviour; she's probably not the fragile flower needing help you think she is, most dogs are pretty darned resilient if allowed to be if you get what I am saying here...
But anyhow, I was once told many years ago that training should be "structured play" and I think this is a really good mindset to get into.