How have you been working on it so far? Has your husband been actively training it too, or just using the command that you've trained? How old is your dog and how long have you had her?
Even if she's practically perfect in low distraction environments, it's much more challenging to get a dog's attention in a high distraction environment like Petsmart. Rather that tell her to "look" when she's probably not going to do it, I'd rather just stand there and simply wait for her to look at you, then mark ("Yes!") and reward it. You could start in the parking lot right outside the car, and when she's consistently looking at you for a reward, take a few steps closer to the store and work on it some more. Gradually work up to actually being in the store. And again, wait for her to offer it, don't ask for it. Giving your dog commands and having her blow you off because there's too much interesting stuff going on is only teaching her that she does not always need to comply.
The more you reinforce attention, the more attention you'll get, even if you don't actually give her the "look" command. This is called a default behavior, and it's something I work on a lot from a young age. For my dogs, a sit and "watch" (my attention command), is a default behavior, so if I'm with them and I'm just standing there doing nothing, they automatically sit and look at me. This has been heavily reinforced over a long period of time, so they know it can work to get them stuff they value - it's required before I open the door to let them out for potties, before I put their food bowls on the floor, before I throw a ball, etc.