The biggest issue on both images is that the highlights on the flowers and the girl have completely blown. This makes the flowers look artificial, like a print, rather than real. The top of the dress, where it meets her neck, has no detail.
The mask is quite hard edged - particularly around the hair and there are some edge issues (look at the curl of hair to the left (her right) of her face). The mask has also cut into her left elbow.
I often add a two layers above the masked insert - clipped to the masked layer below (in the layers panel Alt-Click on the border between the two). The first I set to color blending mode and brush the edges with color picked up (Alt click with brush tool) from the masked image. That deals with any edge colour contamination. The second I set to luminosity and very lightly brush to darken (or lighten) any stand out edges. This often helps the masked image sit better.
The light direction is not a bad match - both look mainly lit from above.
I hope these comments help you.