Thanks everybody
That's why I put the explanation of what rear ended meant
Anyway, my car is a 2013 Civic, so it definitely has airbags. The reason why my forehead hit the steering wheel is because I was stopped at a yield sign, obviously yielding to oncoming traffic, and was leaning forward, watching the cars come. I was probably just a few inches away from the wheel when I was hit, which is why my head was able to slam into it. I don't know how fast the girl was driving, but it felt like a pretty hard hit. Our cars both looked fine afterwards though.