hmm I can see your effort to sell the fist but I'm afraid you're not selling it currently, it just seems she's kind of a shady character and that's why she has that body language. I imagine the moment where she makes a sort of downward punch with her fist is supposed to be when it gets heavy. have it stay on the ground, dont have her pick it up instantly afterwards. when she goes into the next pose, have the arm still dragging behind her, just adding a motion blur there to get it to where you want it to be ereases the heavyness, have the arm slooowly pick up inertia till it gets to the point where she can move it, that's basically what heavy things are, things that need a lot of effort to pick up inertia.
also, dont have it wind up just to end up back on the ground, that is pointless =/ I'd either go from the wind up to the teleport, or simply avoid the windup and have her stand with her back to the camera trying to drag the fist forward and slowly doing it until she finally goes into the teleport
also when she teleports forward, dont hold the position, that doesnt help sell the heavyness, it's just anticlimactic. Heavy things have greater inertia, they're harder to get moving but they're also harder to get to stop, so the speed of the dash should give the fist momentum so that when she teleports forward she can go right into the uppercut...if anything have the fist drag her body upwards afterwards, try to make her look like a ragdoll being dragged by it if you can.
actually, probably showing you something I made would be bigger help.
what happens here with the sword should happen with your fist