This is why a lot of dogs end up crowding and wrapping when when trained to heel. Good for you to want to stop this now.
A few things you can do:
have treats in your left hand, and walk with your hand over his head so he looks up at you. I'm not sure what method you used to teach Maze to heel. Are you looking for a formal obedience/rally type heel? She should be thought to heel maintaining eye contact with you, and that should help switching her focus from the treat bag to you.
Start by holding a treat up by your nose, so she looks at you! Don't bend over to make it easier on her! Stand up straight, expect her to raise her head and work for the treat! As soon as her eyes shift off the food and you get eye contact, she gets the reward. Practice this at a standstill until she gets it. Get her to hold eye-contact longer and longer before she gets a reward. Start introducing heeling with her looking at you (NOT the treat bag! ditch it for now if that helps).
Next step is to hold the treat behind your back were she can't see it, and get her to look at you. At first she will be focused on your hand behind your back, wait it out, say her name very softly, eventually she will switch her gaze to you, wondering why she isn't getting the treat, the nano-second she looks, give her a reward!
Repeat repeat repeat, ask for longer and longer eye-contact. You should be able to get her to watch you (use a "watch me" command) on command without her even looking at the treat. Start introducing a few steps of heeling with eyecontact, treat reward behind your back.
Start with the heel position, no movement: the treat is in my hand behind my back, Falkor is looking up at me, maintaining eye contact:
Then you introduce a few steps of heeling, still maintaining eye contact, the treat is still hidden behind my back. Now Falkor knows full well were the treat is, but he also knows that the way to get it is to keep looking at me.
Notice how nicely he keeps position close to me, straight, head up watching me. At this stage, I'm still bending over to watch him to make sure he keeps looking at me, keeping his attention by talking to him, watching him to make sure he is in the correct position. Later on, I will start walking straight and looking forward like a normal person, LOL! For now, I'm keeping an eye on him to make sure he gets rewarded at the right time.