It all happened so fast. There was no discussion to be had, just pure brute force. But in the brevity of the moment, all Collins remembered was that Barry had swung- his fist or the gun, she wasn't sure -but he had aimed it to the side of JJ's head and the blond boy was knocked down by the impact. 
"JJ!" Collins and Kie leapt forward at the same time in worry for JJ, but Kie was immediately dragged back by Rafe as he scooped her up from behind and carried her away while she thrashed in his hold. 
But Collins was still able to get to him, putting both hands forward and slamming them into Barry's chest in order to push him away from JJ. She didn't really think before she did it, which in hindsight, might've been a good idea seeing as Barry still had a gun on him. But luckily, the force of her push had knocked him a couple steps back and he was too busy trying to regain his footing that he couldn't aim at her and pull the trigger. 
Meanwhile, in a panic, JJ yelled, "Collins, don't!" His eyes were wide as all he could think about was the gun in Barry's hand, and the fact that it was no longer him separating her and the weapon, but the other way around. 
"What do you think you're doing, lil' girl?" Barry accused, narrowing his eyes at her. 
"Don't you fucking touch him." Collins snapped, winding her arm back and swinging with all of her strength to throw her fist across Barry's face. 
Her knuckles made contact with his cheek and sent him stumbling sideways at the impact. It was so quick, he seemed just as surprised as JJ was by the action based on the way his jaw was dropped, but that may have also just been because of the injury she'd caused. Barry's jaw felt like it'd been locked for a split second before he'd readjusted it to its normal function. A sharp pain shot up her own hand from the hit and Collins's fingers fell out of the tightly made fist they were previously in so she could shake off the hurt. She knew that throwing punches hurt the sender just as much as the receiver, but she never knew just how much. She could've easily shattered every bone in her hand. 
While Barry was trying to recover from Collins's swing, Kie was fighting Rafe off on her own. He had her cornered and while she was beating his hands away from grabbing onto her, she exclaimed, "I know what you did. You murdered Peterkin!"
Her words had echoed in the unit, and it was clear that she had angered Rafe by saying the words out loud, because he clenched his jaw tightly and his nostrils flared. There was pure darkness in his eyes as he stared down at Kie and his hand shot forward to wrap itself around her neck while digging his fingers into her throat. "Don't you ever say those words again." He growled. 
Collins had been too busy watching the whole scene play out that she hadn't realized her back had been turned on Barry. He used what was going on with Rafe and Kie as a distraction, and just as he was about to strike while Collins was caught off guard, JJ jumped at him and tackled Barry to the ground before he could make a move. 
Almost at the same time, Collins lunged forwards in the direction of Kie and yelled, "Let her go, you psycho!" She threw her arm around Rafe's neck and squeezed as hard as she could while pulling him back so he would release his grip on Kie. 
For a moment, his hands did loosen their hold on Kie, and it was enough for her to wiggle out of it and gasp for air, but it still felt like he was blocking her airways. Rafe's nails dug into Collins's skin as he clawed at her arm to get her to let him go, but she tried her best to lock her arm around him and turn a blind eye to the pain. His face was beet red due to all the blood that was rushing to it as his body begged for oxygen. It wasn't until he fell back into the side of the boat, sandwiching her in-between, did he finally get her to slacken while she stumbled onto the ground.