A woman can type "I hate men" while being with a man because, for women, "I hate men" means "I hate rapists, potential rapists, fuckboys, and ill-mannered men." That phrase does not refer to respectable men(it's hard to find).Maybe her partner is none of those things.
If as a man you ask to see your girlfriends’s pad as proof that she’s really on her periods, understand that you don’t respect consent and that you're a rapist.