I asked my girlfriend of 5 years what her preference is to my facial hair and she said she did not have one. In the past, I've always been relatively clean shaved when we've gotten together. Does she really have no preference on how I shave my face?
She would probably let you know if she hated some styles of facial hair (no shave november didn't work in my book!) but is probably indifferent to the styles you have done. If she ever strokes your face more than usual when you have a certain look, she might like the look or feel of that. I love touching my boyfriends face when it's extra smooth, maybe she's the same way. I really don't notice a big difference though between just shaved and haven't shaved for a week, so she probably doesn't mind either way.
That is a possibility. But think back, if you tried something different to your facial hair in the past, did she react differently? A little more cuddly? If so, maybe she does have a preference and just doesn't want to seem like she is trying to change you into what she wants. If she didn't react, she probably doesn't care either way. If she reacted negatively...well, then she didn't like it.