Do you randomly reward her during the day for looking at you? If you are clicker training, you should have your clicker and treats on you all day to take advantage of her offering behaviours you want to develop.
Also is you are now trying to extend the focus to more than just a glance, as soon as she looks away, get her attention back at you quick by softly talking to her. When she is looking at you, praise and talk to her to keep her attention on you - but as I was saying, one to two seconds is a good way to start, and I would stick to that for now until she understands and offers the focus on her own, and slowly work up from there.
When I do focus work, I only expect a second or two of focus for the first week, and then slowly move up the amount of time adding a few second a week.
All of the above!
This is exactly what I do - I want a very strong default "watch" without having to ask for it, as well as be able to get my dogs to watch me on cue.
I'm not a fan of luring up to my face, because as you've noted, it's hard to tell if they're actually looking at YOU, or the food right next to your face. I start by holding the food with my arm hanging at my side, or even holding it out in front of pup's nose. I don't say a thing, I just WAIT. It can take a little while for the pup to stop trying to get the treat and to look away from it, but being super food driven (Halo is exactly the same way!) I think works for you in this case because she's going to be highly motivated to learn how to "make" you give her the food. And with the food down low, it's very obvious when puppy looks away from the food and up at your face. Mark that split second and reward.
Until you can hold out a piece of food and her head immediately whips up and she give you eye contact, consistently, every single time you do this, I wouldn't worry about extending the amount of time. I also do what Lucia suggested, capturing eye contact whenever it was spontaneously offered up by the puppy. I wear my treat bag all the time for the first few months with a new puppy, it only comes off at bedtime when they go in the crate. My bag has a metal ring, like a keychain, and I can attach my clicker to the ring with a small carabiner. I also have a wrist coil, but sometimes it's easier to leave it on the bag, then click and reach into the bag for a treat at the same time.
The more she's rewarded for looking at you, the more she's going to do it. To build on that, make eye contact work for EVERYTHING. Again, don't even ask for it, just wait patiently, then mark and reward. Going outside (once she's housebroken), coming inside, getting in the car, getting out of the car, coming out of her crate, before being allowed to eat, before getting a bone or chewtoy, before throwing a ball, before taking a toy, anything you can think of. In this case she's getting real life rewards, giving her access to valued resources rather than food.
At some point when you're pretty sure she gets the program and will reliably look at you under certain circumstances, give your verbal cue for the behavior right before, then mark and reward the second she looks at you. Work on it to where no matter what she's doing you can say "watch" (or whatever your cue is) and her head immediately whips around to make eye contact, and THEN start working on extending that by a second or two. There's no point in trying to get her to look at you on cue and hold your gaze for 4 seconds until you know she fully understands the cue in the first place.
I also do what Lucia does, I let them know that they're doing the right thing by talking to them - "gooood, that's it, nice job, excellent....", and if they look away before I mark and reward I might say "ack!" or "oops!" and when they look back I continue the praise. You don't want her to think that because she hasn't heard the click and gotten a reward that she's not doing the right thing. I use my voice and facial expression a lot too, to show that I'm happy and pleased with them.
I can't remember - have you been doing the It's Yer Choice game with her? That will show her very quickly that she needs to ignore the food and look at you in order to get the food. I practiced a short time with Halo every day.