Thank you for the reply, Teeki. It's definitely abnormal. The thing is, aside from not wanting to unnecessarily alarming her, she's never been one to go to the doctor. For any reason. Silly, I know.
Last night as I rubbed her feet and asked her about her day, she seemed to be more comfortable, in less pain and whatnot. So, whatever it is, it seems to be subsiding.
Her period usually lasts 5-6 days, starting 21-22 days after the end of her last day. Honestly it's been this way since I've met her. This is the first time she's ever really experienced anything like this since I've known her at least. When I questioned her about it she states that she couldn't remember this ever happening before, but maintains that it is definitely her period. In fact, it's her tendency to be so adamant about this being only an extremely early period is one of the reasons I haven't stressed going to a doctor. I figure a woman really knows her own body and if nothing extreme or emergency-room visit worthy is happening, I'll let it be.
If this does happen to be a miscarriage or implantation bleeding, would her regular cycle resume? That would mean that she would start menstruating on January 1st or 2nd. If she misses that, would that be a sign of anything?