Personally if the meet turns out to be good, I'd pretty much ignore the rescheduling completely - although it would get a mention in the review. Sometimes shit happens, and (assuming honesty) I'm sure you'd rather she rescheduled than go through with a meet whilst she's on a period.
However, if it becomes a habit then that's definitely something that needs considering - I've had a regular girl in the past who made such a habit of rescheduling (for believably genuine reason) who only got a Neutral review despite the fact all the meets that happened were great. In the end it was her lack of reliability that stopped me seeing her completely, and had I done a second review of her it would definitely have been Negative.
In your case. giving her the benefit of the doubt probably makes the most sense for now.
EDIT: In the time I took to write that, you added your extra post. I'd say it's heading towards a Negative - but I'd still only do a single review for the whole experience. If you persist and a meet happens that turns out well, I'd be considering a Neutral. IMO, she's gone beyond the point of Positive being an option.