Actually half the Einherjar went to Freyja (I believe she got first pick, but don't quote me on that), the other half went to Odin. I recall reading that those who died while fighting in defense of something went to Freyja, the attackers to Odin.
I don't believe they would only pick up male warriors, but female ones would have been relatively rare I think, at least back in those days.
I believe disir is the correct term for them, female ancestral spirits.
The afterlife for those chosen as Einherjar would be to fight all day, and at sunset rise up (if slain), and to feast all night. That is referenced for Odin's Einherjar. I don't recall anything specifically around Freyja's, but considering the Einherjar are training for Ragnarok, when they will fight alongside the Gods, it'd make sense for them to be doing the same.