Just be careful with vests I almost lost a dog because of one. Some how a branch off a stump got up in it. Dog couldn't get loose and almost drowned. I got out to it just in time. Vest was tight on him too. I have read on another site that there have been other dogs that weren't as lucky as mine due to same thing happening. Freak accident's but never want to lose a dog that way. I still use one when it gets real cold. I just watch them close now.
My dog wears a neoprene vest when hunting. I think it helps some with warmth, but the other reason many use them is because many vests are reinforced in the bottom and provide protection from getting stuck by submerged branches and such when jumping out of boats/blinds. However, if your dog is getting that cold this early in the year, you may have to take a two pronged approach:
1. A good neoprene vest with help. 2. You may have to take a large towel and dry her between retrieves. I know this is tedious but you may not have a choice.