It does make a difference that it was a 4x4. For a start, it mounted the pavement far more easily and quickly than an average sized car would have done and continued its momentum - if this vile woman had been in a different car, the impact with the pavement might have stalled her or slowed her down and she might not have hit the buggy. Also, once she had hit it, it might not have become trapped in quite the same way as it did, when she rammed it again and again making the death of the little boy inevitable.
If she was drunk, she won't just get off with a fine, she will definitely go to prison and quite right too. Unfortunately, she won't go for as long as she deserves because for some reason killing a child with your car is considered more acceptable than killing one by any other method.