It really depends on the dog. And if you adopted your second dog from a shelter or rescue she could have some past where she wasn't given enough food or food very often so she eats like she doesn't know when she'll get more.
I have three dogs. Two of them would eat and eat as much as they could if allowed. When they do get food it's gone in a flash. They'll go to their bowls from time to time and lick them, look at us for treats, etc. But when they're really hungry close to feeding times they'll whine at us.
From what you've written it doesn't sound like your dog is doing anything completely abnormal. As long as she's healthy (up to date on shots, you know she doesn't have worms, etc.) I'd just keep monitoring it. It could be something she'll always do as part of her personality.