My lab is seven months old. 28" around the chest. Large vest goes up to 28" Extra large 31". Loose fit isn't desirable as a tight fit isn't. Which way do I go? Will she gain much in girth?

I would try and hold off til your pup fills out.

I agree, you will waste money if she grows out of it.

My only concern is she is pretty light colored and I want to minimize flaring birds.

Dogs don't flare ducks. People and boats flare ducks. If you plan on hunting her at seven months old (which I would strongly discourage) then get the vest that fits her now and then buy the size she needs when she's a full grown dog.

My best dog I hunted at 6 months and she was better than the two and three year old she was hunting around. However I am concerned about learned bad habits and stuff so the jury is still out on in. Honestly, with an unfilled trophy tag still she has yet to be in a blind. I may take her on a hunt or two but it will not be in a situation with a bunch of hunters or pressure. Me, a few deres and if we are lucky a bird or three.