Ahhh, rationalization. Seems to me that part of you saw the damage to the bumper and were not too disappointed about it. It rationalizes the purchase of the new bumper... I know all about it.
It is cool of you not telling your mom though. I'm sure she'd feel really guilty knowing she cost you money, especially when you were nice enough to lend her your car in the snow. But onto your question: I think the M-Sport bumper is the best option - especially if you're only getting the front bumper. I like the Rieger, but without the side skirts (which I don't like) it wouldn't look right.
You might also want to consider how low to the ground all 3 are before buying - especially if you deal with a lot of snow.