Cool image and you've done a good job with the lighting and camera matching, from a observation purely based on the background and what i can see, she does not appear to be casting any shadow would expect to see something, as she is blocking the light, and the rim of the bath is still lit....and your background image is pretty much in focus from the foreground to even the very distant ones, go lots of detail, so she looks a little out of focus, not quite sharp enough to match the surroundings......

She's beautiful... I agree with Darkglass… the shadows seem a little inconsistent. Based on the shadows in the grass to the right of the tub, her back and the tub rim behind her should be in shadow.

thanks for all the feedback. It helped a lot. The render was too grainy, the camera angle wasn't quite right the sharpness was greater in the background than in the render. the exposure and contrast was wrong. The mask around her hair was not soft enough. the Hair leaves a sharp shadow on her face that should not be there.

The main offending was from the background as it was shot with smartphone. The amount of visual distortion from that lens and the software oversharpening is difficult to reproduce without creating a new template. Something that I will have to do. The sharpening problem is more difficult to fix, I have to turn it off on the phone somehow. I tried sharpening the render, but it increased the grain considerable. I tried to add more grain to both the images, but again I got disproportionate grain.

My previous image, I did very little to as BG was on a dslr, and the FG was rendered with more time learned my lesson. But sometime you just don't have a DSLR to use...

It might not apply here but I put the background on a poster prop and then adjust rotation, scale brightness and camera and render in one step - then no postwork needed. I usually make a non rendering wire frame ground to help get perspective right and catch shadows when needed..

Excellent

Darkglass already mentioned the issues so I won't say it again. As for the grain, I guess Poser needs to add the Denoiser like the others have added now (Daz, Octane, etc). It really helps. Instead of using photos, try to use assets and materials from Quixel Megascan or similar. They are based on real life and using them will give you realistic scene plus the shadows etc. will be proper as all the elements will be within your poser scene and lit by the same light.