I can't seem tell if she just pulled or is going to shove the mechanical heart into something/somebody.

I'm not sure, but I keep seeing this as a parody, either of Simon jamming in the Core Drill, or of Domon Kasshu preparing to use the Shining Finger.

Given it's a heart, probably Gunbuster.

Definitely gunbuster. Needs more ripped shirt though.

Missing her left arm. She's a robot. Or an android. ... Something to that degree. Cyborg..