Okay - so our labradors are not fatties - well, not after a few months after re-homing them! Our collies usually are “not sleek” so we are probably meet in the middle.
How do we do it - exercise, feeding and rewarding.
Increase the length and pace of her walks. Labradors can tolerate the same exercise level as border collies - my flatmate’s labradors often came out with me and my collies. They just rock along at quite a pace. Recently, I was walking only one of the labs and noted that we were doing 10 minute 5 second per kilometer on the flat!!! Albeit he could do the same on hills so …
Summer its swimming in the afternoon - it’s great going in our rivers with a nice strong lab to drag you up the river. It is also quite rewarding doing interactive activities with our dogs. My collies learned to love swimming from the labs
Do not use food as her reward (if you do) - move towards play or praise. (Pretend that she is a collie that have been bred for centuries to work all day for a “good dog”.) My flatmate found that her latest rescued lab was just looking for the scent of the liver treat rather than the scent that he was supposed to be. He LOVES his pats and cuddles as the reward. I am using the same with all of my CGC classes now. It is quite amazing how many dogs actually do love praise and being told that they are a “good dog”.
Feed her according to the weight that she should be not what she is. And, given the recent publication on the extra gene … So, if your vet reckons that she should be say, 32kg, then feed according to that. Not what she actually is. You can also throw in leafy green veges such as spinach or cabbage or celery or carrots.