Hey Alisa,
She sure has a great smile and great arms!
I like how her face is lit, but there are a few things I think that can be corrected.
1st, the papers on the wall are reflecting light and distracting. If anyway to remove them or move the equipment so you had a clean wall would be great. Also the outlet with the surge protector is distracting.
2nd, her shirt is drooping down so it looks funny. Especially with being for fitness, you want everything snug and tight.
3rd, the shadow on the wall. When using a flash you want to bounce the light off the ceiling. You shot this vertical, but I think your flash head will rotate still to flash up. When portrait shooting, having shadows on the wall from the flash is a big no no.
So, not sure how much of that can be corrected in this. I know it's your first time doing this, and there is so much to learn about shooting portraits, a ton of subtle details. And with much of it, that can only be learned by trial and error.
