Okay, so I have always wondered this, what does Edward do when Bella (before she becomes a vampire) do when shes on her period??

I am positive that, unless he has been starving for human blood for a century または more, ヴァンパイア would not quench their thirst with menstrual blood.

This what Stephenie Meyer 発言しました
Q: Several girls wanted to know if Edward would have a もっと見る difficult time being around Bella when she’s having her period.
Answer: Yes, a little bit, but he would never say anything about it–much too much of a gentleman. And Bella would be way to embarrassed to ask. (It’s not the same as a cut, though. It’s sort of "dead" blood, if あなた get my meaning)"
From the website
link
Hope it helped :)