This is my editing process in photoshop step by step. First I opened the image in photoshop:

I used the clone tool to get rid of the background mess to ensure that the background is completely white (or as white as I can get it):

I then used the levels tool to darken the model and to whiten the background to pure white. (using the sliders from both side of the levels). I made sure I did not completely blacken out the model though as I want some colour to still show:

In this case, the colour in my pictures left a blue/purple haze which I really like.

I then created a new file with square dimensions so I could transfer the silhouette to it which will leave me with a square image ready for making my collage:

I used the lasso tool to select the silhouette and copy it to a new layer:

I then dragged the new layer to the square canvas and resized the silhouette so it fit inside the square:

And I was left with my fully edited image! :)