Should I change my recall word?

My 18 m/o female lab is, of course, a Very Good Girl. On leash – short, long, retractable – she comes whenever I say 'come.' We have trained a lot that way. When she knows it's a training session and that I have treats and she's off leash, she always comes when I say 'come', even though she knows she won't get a treat every time. We have trained a lot that way, too.

BUT when she's not on the leash and it's not a training session, she has more selective hearing. In the woods, a yummy smell might make her less interested in me. First time on a walk that she does that the leash goes back on and she's fine with that. In the house, even, when it's time for her last walk of the night – she knows the routine and it's the same time every night – sometimes she just looks at me when I call her. As soon as my hand is on her collar when she doesn't come she gets up and happily follows along.

Do I need to start over with a new word, since she has figured out that when she ignores me there's no terrible consequences? Or is there something else I could be doing to get her to be more responsive to 'come'?

If it matters, she is a poster child for responding to other commands, like sit and down.