you should add some up and/or down movement and also some secondary action(s) like hair and/or breast bounce. you should make the skirt move forward and back with the legs. and you should make the arms swing forwards, right now it looks a bit like they are rotating around the body since her right arm is never going forwards.
I would recommend looking at how the lemmings are animated since they are the closest in size with a similar amounts of frames in the walk cycle. most other characters with a similar pixel count (like small mario on nes) only have 3 frames of animation
also just for general animation help I recommend the book The Animator’s Survival Kit. I don’t think it ever talks about pixel animations but the principles are all the same