ok, so i tried again today!
First things first, I am not shooting indoors with a flash/bounce. I am shooting outside in nice afternoon light. I set my iso to 250/320/400/640 and even 800. I tried shooting at f2.8 and sped up my shutter speed to 250, and 400, even 500 still only a few shots were sharp! And only in the cases where she was somewhat still, anytime she was in any kind of motion, the images are either all out blurry or soft. I tried continous shots instead of one shot. I did not try al servo though. Its almost as if the AF is either too slow, or even though the red dot is on her eye, its focused on her nose. I am maybe 5 feet away from her.
I tried testing the lens by shooting my husband holding perfectly still at f7, and mostly sharp but a few soft, but once i had him walk towards me, even at f7 and 400 at iso 640 the images were blurry. I am baffled as too why i can't seem to freeze the image. When I use this lens on a tripod for tabletop macro work, its sharp as can be, but when i want to use it for portraits i'm running into such an issue?
My recommendation would be to work in M mode with auto ISO activated. You need to set your shutter speed (1/500 or faster), your aperture (f2.
and let ISO get whatever it needs to get to ensure enough light reaches the sensor. That's what auto ISO is for.
In terms of AF, yes you of course need to set it to C mode to tell your camera it needs to track the subject, but I am sure you know that. Another possibility is that you are reaching the limitations of AF of your body + lens combo at close distances. Once again, macro lenses are not designed for AF tracking.