It's common, even for a well-trained puppy, to develop behaviors like digging or go through a wild or disobedient period in their teenage stage.
It depends on what kind of training you're talking about. If you're talking about training her not to dig or chew, and she's digging and chewing, yes you need to go back to the basics and STOP her from doing these behaviors immediately, because they're self rewarding, and the longer she does them, the harder they will be to break out of her.
If you're talking about basic commands or foundations for work or sport....you'll only need to go back to the basics if she hasn't been using these or has forgotten them or gotten unreliable in listening to commands. If you ask her to lie down and she does every time, that's an entirely different issues than digging/chewing.
You say you don't have time to train her, but is she getting enough exercise/stimulation or as much as she used to? If not, that's probably why she's digging and chewing, and you need to figure out how to make time to keep her occupied, or you're going to have a very big problem on your hands.