@justinkapur - firstly, what lens or lenses do you have with that Canon? Ideally you would use a fast prime (i.e. not zoom) lens around 35mm (for a DX camera) or 50mm (FX camera).
Set the camera to "aperture priority" and set the aperture to the widest opening (i.e. lowest number - really fast lenses can go down to f1.4 or even lower). This means a narrow depth of field - you will be in focus, but anything closer or further away will be blurry, which is ideal for portraiture/subject photography. It also has the advantage that lots of light enters the camera, so you can use a faster shutter speed, which means less chance of blur if Muggins doesn't know how to brace themselves for the shot.
A lens like this will also have virtually zero barrel distortion (which is what's making you look portly in your current photos).
Most importantly, go outdoors at lunchtime for the shoot. Look at my gallery, or Urban C's, for framing ideas. A set of stairs, or a door opening, or a footpath, all work. Avoid direct sunlight, and make sure the sun is behind Muggins, not in front of her.
On your marks. Set. Go!