Her Heavy Arms work on ball joints, can rotate and whatever through the power of imagination, and are two meters long. They move independently in regards to the rest of her body, I imagined, which is why she can do 'hand-to-hand' attacks that are impossible for humans to normally pull off (e.g sweeping side to side with both Heavy Arms while her body is spinning vertically). 

All things considered, she would have been fine with cannon-balling straight into Newt as well.

Of course, if Lucius wants to nerf that, I'll do some post-reimagining then, and if my post was unclear, I apologize, and will make OOC effort to clarify her arms' oddities in the future.