Ways of handling a backlit subject 

Camera metering-evaluative as per the camera's suggested metering

since the background is bright due to the outdoor light as well as white of the curtains, the subject has been rendered dark. the camera is reading the bright light as well the white, thus underexposing the main subject.

Shooting Mode Aperture-Priority AE / Tv( Shutter Speed ) 1/160 / Av( Aperture Value ) 5.6 / Metering Mode Evaluative Metering
Exposure Compensation 0 / ISO Speed 100 / Lens EF24-105mm f/4L IS USM / Focal Length 105.0 mm / Flash Off

+1 exposure of evaluative metering

To override the camera metering exposure compensation option was used in the camera, which resulted in beter exposure for the subject

Shooting Mode Aperture-Priority AE  /  Tv( Shutter Speed ) 1/125  / Av( Aperture Value ) 5.6  / Metering Mode Evaluative Metering / Exposure Compensation +1  / ISO Speed 100 / Lens EF24-105mm f/4L IS USM / Focal Length 105.0 mm  / Flash Off

Spot metering from the centre of the frame with +1 exposure compensation

Instead of the evaluative metering it was changed to spot metering with plus one (+1) exposure compensation'

Shooting Mode Aperture-Priority AE  / Tv( Shutter Speed ) 1/320 / Av( Aperture Value ) 5.6 / Metering Mode Spot Metering / Exposure Compensation +1 / ISO Speed 100 / Lens EF24-105mm f/4L IS USM / Focal Length 105.0 mm

Flash Off

Spot metering from the subject with +1 exposure compensation

This time the focusing point  was overlaped on the subject and then recomposed to get the existing frame. Alternatively the focusing point on the right of the frame could have been selected. the spot metering coincides the focusing point chosen. Besides the right spot metering the exposure is also +1 of the exposure value.

Shooting Mode Aperture-Priority AE / Tv( Shutter Speed ) 1/50 / Av( Aperture Value ) 5.6 / Metering Mode Spot Metering / Exposure Compensation +1 / ISO Speed 100 / Lens EF24-105mm f/4L IS USM / Focal Length 105.0 mm / Flash Off

Bounced flash -evaluative/matrix metering

Two things were working against the shot. The bright outside light and the white curtains. For this shot a flash (580exII) on camera was bounced from the white ceiling of the room with the flash card out.

Shooting Mode Aperture-Priority AE / Tv( Shutter Speed ) 1/200 / Av( Aperture Value ) 5.6 / Metering Mode Evaluative metering / Exposure Compensation 0 / ISO Speed 100 / Lens EF24-105mm f/4L IS USM / Focal Length 105.0 mm/ Flash On / Flash Exposure Compensation 0