She's made excuses for him and covered up after him. That must have been frustrating as all hell, especially if she suspected, like me, that he and his team are doing it deliberately.
Look at what happened this week. Ardern made a show in Parliament of ruling out further regional tax hikes as long as she is PM. Should've been a big win. Nek minnit Shane Jones, aka Mini-Winston, stood up and said that was the first he heard of it. Talk about throwing his own PM under the bus.
Ardern spent the next day mopping up after Jones and assuring everyone that it was long-planned. She could've returned the favour and thrown him under the bus. She didn't.
The Prime Minister is the Government's biggest asset. She was obviously inexperienced a year ago and her mistakes showed that. She should've been steelier sooner, especially with her discipline of mistake-prone minister Clare Curran.
But, with time, Ardern's settled into the job. It feels like hers now. She can flit from steel to warmth in a breath. That's a winning combo in a political leader.
Ardern is popular on the world stage and climbing the domestic preferred PM polls.
Peters also deserves credit. Even though he's undermined the PM on refugees, employment relations changes and three strikes law repeal, it doesn't seem to be done with malice. More, it looks like a smart political move. He's positioned himself as the barrier preventing the Government leaning too far left.
His critics can quite frankly eat their socks. Anyone who said Winston wasn't up to the job of running the country has been proven wrong. His six weeks as the PM's maternity leave cover were probably the calmest period of the last year.
It's not a surprise that these two have made the coalition work. Peters is charming and respectful in an old-fashioned chivalrous way, which means he can be especially gracious to women. And Ardern is charming and respectful too, which will get the best out of Peters in the way a tummy tickle gets the best out of a cat.
In this column a year ago I predicted that there were four challenges facing Ardern: The Greens dragging the Government left, the little infrastructure time bombs National had left lying around, team Labour's inexperience and Winston Peters' love of the limelight.
All four have proven true. But Peters is Ardern's biggest challenge, because she needs him the most. As predicted he's competing with the PM for attention. He's extracted huge spends out of her as dowry for his coalition support. $2.3 billion for war plans, $1 billion for diplomats and Pacific aid, $3 billion for Shane Jones' regional slush fund.
And, looking ahead, Winston could be one of the PM's biggest problems in the remaining two years of this government. He knows how coalitions can kill off minor parties. If you want to survive as a smaller party, you have to fight for all the attention you can get. Even if that means embarrassing your own coalition partner.
He's already done it three times in one year. This isn't even an election year. Imagine what kind of a frenemy he'll be in 2020.