My two cents: I think it'll be Abraham, purely because of the build-up he had in the episode - it seems highly likely that it'll be someone in the RV since Trevor from GTAV pointed it it'd be their "Last Day on Earth". Plenty of evidence pointing to Glenn too, POV shots in particular. If the shadow passing Rick's face is to be believed then Eugene is the other strong possibility.
I'd be amazed if they killed a woman that way - women very rarely get gruesome deaths on this show.