I think I see where Amber is going; if this is the beginning of dominant behaviour, your puppy could be trying to test her boundaries by trying to control your wife.
Again, the trigger could be any of the things that Amber mentioned...
It could just be that your pup is getting a burst of energy in the evening. My pup used to do that too... (still does at times).
He doesn't bite me, but sometimes he'll just get into a frenzy late at night where he grabs a toy and shakes it, throws it, chases it, attacks it, barks and growls at it etc. etc.
This pops out of nowhere; he'll be lying at my feet for several hours while I study or work on the computer, and then all of a sudden he wants to play and goes nuts.
It might just be a pent-up energy thing. My pup always gets plenty of exercise and training during the day, so in theory he should be tired out. Then again, who knows what goes on inside their brain? hehe
Ed talks about this on his dominant dog DVD and demonstrates the behaviour you described with a really cute little corgi pup.
Basically, your first response is to redirect your pup's "aggression" to a toy. Teach her what is prey (appropriate chewing items) and what isn't (you or your wife in this case).
Pick up a stuffed toy or a rolled up towel or something and wave it in her face; encourage her to bite that when she bites hands.
If she gets too wound up and aggressive, grab her by the sides of her face, hold her still, look her in the eyes and repeat NO, KNOCK IT OFF in a very very calm, firm voice.
The idea is to force her to be still for maybe 10 seconds or so while you very quietly and firmly talk to her, just to settle her down.
If she's too squirmy, get a hold of her by the shoulders, quietly pick her up off the ground and again, look her in the face and talk to her calmly and firmly under she stops struggling.
It's important that you (or your wife) stay perfectly calm when doing this. If you get upset and start shaking her or raising your voice, you'll just make her more frenzied.
No need to shake or grab her scruff.
This immobilization method is very effective. I tried it out just as Ed demonstrates on his DVD with my pup and it works very nicely. Ok, now he's 10 months old and 95 pounds so I can't really "lift" him off the ground anymore, but I'll tell him to lie down and stay.
Just putting him in a down stay for 10-20 seconds while staring at him and telling him to CALM DOWN in a quiet firm voice is usually all it takes to calm everything down
It gets a lot easier when you do this for a few months.
In your case your dog isn't going to be getting a whole lot bigger, but if you let her get away with this behaviour now, it'll get much harder to control later on and could escalate into full-blown dominance.
Young pups get crazy, it's part of their charm.
The first few times, it may be hard to calm her, but if you stay perfectly consistent and calm, and don't let her get away with it, it'll get much easier to stop as she gets older.
Sometimes on our off-leash walks at the park or forest, my pup gets overly excited and will start to harass my older female shepherd (11-year-old) by charging at her, and jumping on her and body-slamming her.
Of course I don't tolerate this at all, not for a second, but I find that giving prong corrections for this is sometimes counterproductive (makes him even more hectic and he'll start to bite me).
Luckily I've worked with him on the calming method since day one, so he knows the drill. I don't get angry or upset at him, I just say DOWN in a no-nonsense tone (which he obeys on the spot, his obedience is excellent, I'll give him that
), and I stand there quietly for a few seconds.
I talk to him in a firm calm voice while maintaining eye contact, but there's no punishment or correction involved.
After about 15 seconds, I walk up to him and very quietly praise him and release him.
That's all it takes. If he goes over to my older female again, I can just say NO and he's calmed down enough to back off on command.
Just taking the excitement out of the situation is really all it takes to put you back in control. The air of superiority that you give off to the dog by remaining completely calm and in control of him will go a long way in establishing and maintaining your status as leader, too!
Anyway, if you give us more information on your pup and on what exactly goes on (what triggers her, how you and your wife deal with it), maybe we can give you more specific advice, but the most effective thing (especially for a young pup like that) is to just get her to calm down a little by forcing her to stay still.
Once she knows a sit or down stay you can use that, but in the meantime, just pick her off the ground (not pick her up and holding her against you and hugging her!! pick her up so her back feet are dangling) and wait till she settles down before putting her back on the ground.
Good luck, and enjoy the puppyness while it lasts... they grow up too quickly