And is Shaw that kind of scientist? No. She doesn't have faith in the unknown because there is nothing unknown about her beliefs. The Engineers created life on Earth? That must mean God created them. That's not faith in the unknown.
You are jumping to conclusions and your bias is showing. It seemed very clear to me that Prometheus was specifically vague about Shaw's faith. She wears a cross, which is predominately seen as a Christian symbol today, but didn't originate with Christianity, nor is Christianity ever directly talked about in Prometheus. I think a cross was used simply out of convenience because it is so easily recognized and associated with faith, not to denote a particular viewpoint held by Shaw. She also never talks about "God" and only, like a scientist, asks questions, such as "if the Engineers created us, who created them?" Now that presupposes that for something to exist, it has to have been created instead of the presupposition that it mystically appeared from nothing, but again, scientists come up with theories like this all the time and their belief in them, when they cannot be proved IS an example of faith. Again, I am not arguing that Shaw is a great scientist, because she is horribly compromised, but her hypotheses aren't as unscientific as you are making it appear to be, especially considering (in the universe of ALIEN) that her hypothesis about the Engineers was correct. Is she right that someone else created the Engineers? Who knows. Maybe we will find out in Paradise.