It's not confirmed, but it looks like Jessica Alba had a nose job around age 20. In this before and after photo, her nose looks wider all the way from the top of the bridge down to the tip. It could be argued that the overexposure of light is making her nose stand out more, but it just seems bigger.
Once again, the contours of her nose look a couple millimeters wider in the before photo. However, the dim lighting in the after picture minimizes the contours and shadows of her nose.
If Jessica Alba had plastic surgery, it was just to make the bridge and tip slimmer by 2 millimeters tops. Nose job or not though, she's still one of the most beautiful women in Hollywood.