"I must commend you, Scamander," said Grindelwald, "I could not have found the first clue without you. Now, you and your friends will lead me to the next one and be greatly rewarded with chocolate treats!"
"We will NOT!" Newt responded with dauntless courage and a little regret that he wouldn't get any of that sweet chocolate.
"Then you will do it as my prisoners!" declared Grindelwald, raising his wand. "Expelliarmus!"
Newt's wand was knocked out of his hand. Tina raised hers at Grindelwald.
"Expelliarmus!" said Mole, and Tina's wand flew out of her hand as well.
Nagini didn't do anything because she's a pointless character, and no one noticed her anyway.
Meanwhile, Grindelwald raised his wand and cast a spell that tied up Newt, Tina, and Jacob. Using side-along Apparition, he and Mole left with their prisoners, leaving behind Nagini, whom they hadn't noticed at all. In fact, we've forgotten about her already, and this here is the last time Nagini will ever be mentioned in this story.
By the way, it turns out that Newt would #StandWithMaya if he was living in 2019. This is canon now.