I'm not a trainer, nor into hunting, but I've had a bunch of dogs that I've successfully trained myself.
You've had dogs before, so I don't mean to sound like you don't know what you're doing....but I have a couple of questions/comments that may allow a better understanding for those who are more professional in this endeavor.
She's four months old. That's young, regardless of how well she seems to be trained in certain ways.
When she's backing away from you, does it seem to be out of fear or is she angling to make play-time out of it? (I'm hoping for play-time.) If fear, does she do it around everyone, or just you? Some Labs seem to be much more sensitive/anxious than others. My fetching girl was hyperactive anxious with no fear of humans. (My 1/2-Lab female mutt didn't fetch and she was passive/anxious....her watered-down Lab offspring loved to fetch until his joints started acting up too much. He, also, is passive/anxious. Neither of these dogs had/have a fear of humans.) My Labby boys had no fear of humans, either, unless you count Hershey's anxiety when the ear drops came out. If her only fear is of you...perhaps you are more heavy-handed than you think. Or perhaps your voice is sterner than she likes. (I have an assertive, not angry, way of speaking sometimes and neither of my two passive/anxious mutts are always comfortable with my voice....even if I just have to speak a bit louder for someone on the phone to hear me.)
Some Labs don't like to retrieve. My female did...she was a fetching fool until she started having problems with overheating/seizures. Two of my males (a choc and a yellow) did not. (My third male had structural issues early on, so...who knows?) I never got those two males interested in fetching/retrieving...though one would play keep-away with our female Akita (Akitas don't fetch).
Hopefully, someone with more experience in training will chime in...especially with hunting expertise.
Good luck and welcome to the board!