That's just one of many areas where readers/viewers willingly suspend disbelief.
Superman is supposed to be able to do that; that's one of the benefits of being beyond human is (for him). A literal reality distortion field is actually the best explanation for all of the exceptions to physics that happen around him; Lois passing in to that bubble while being saved is just one more thing on the list.
Well done, Superman, you just broke your girlfriend into three pieces with your arms.