Considering that you seem to be struggling at least in your own mind with making a selection, you might want to consider trying U Point technology. You can see a great demonstration of it at the Nikon Capture NX2 website without having to download any software. Nik Color Efex Pro also has it, though I don't remember if it works as a stand-alone product or as a plug-in with Lightroom. The last time I checked, it didn't work with Elements. You may or may not find it easier to use U Point technology to make selections.
The light in my photos is far more diffuse (less contrasty) than in your photos. You might be surprised to learn that my photo that you and I liked best (thank you!), along with the other photo that others liked best, had a gentle S-shape in the curve that increased the contrast.
Considering that your photos began with more contrast than mine in the scene, I post-processed your image to reduce the contrast on everything except the subject. I then increased the contrast on the subject and added Local Contrast Enhancement to it (just the subject). For me, the white flower in the bottom right corner was distracting, so I used the Curve to darken its mid tones and I used Gaussian blur to render it more out of focus.
Part of the reason for displaying all three curves is to perhaps open your mind to using the Curve tool for various purposes. It can be used to accomplish whatever goal you have, not just to increase contrast, and it can be used very effectively to alter only part of an image.
Curve applied to everything except the pink flower in the front and its stem
Curve applied only to the pink flower in the front and its stem
Curve applied only to the white blossom in the bottom right corner
The final result (intentionally overdone just a bit to demonstrate the effect of the various curves)