My girlfriend was going through something that women often go through but I didn't notice.
Are you talking about menstruation?
Well, I didn't notice it at first but now I do
Sometimes we miss stuff for no apparent reason. We are only human and not some hyper tech android from the future.
She seems super emotional now. My roommate gave me a pamphlet on it but I don't know if it's okay to ask her.
It's fine that you didn't notice it right away, and now that you know you can talk to her about it. If she's your girlfriend then you can talk to her about her mensuration to learn more and show that you care about her.