I'm a totally disabled as a result from my combat PTSD. I go to my local VA most days of the week for various treatment for my psych issues and I rub elbows with a lot of other coocked-out vets. I've also attempted suicide several times.
I don't have any data to back this claim up, but I immagine that a large portion of women in the VA struggling with PTSD and suicide are also victims of sexual assault while in the military. I can't speak from personal experience, but I'd imagine that there is a lot more shame surrounding a sexual assault than being a combat vet and that in turn impacts whether female seek treatment or not.
Also, as I understand it, many female vets who have been assaulted find being around lots of males (especially the military sort) to be a trigger for them. That only further serves to be an obstacle to treatment for women - especially at the VA.
I don't mean at all to suggest that there aren't women who are combat vets with PTSD. Although I was an infantryman (there were no women in the infantry when I was in) there were women in many supporting roles who were doing daily convoys and patrols. I had Bradley Fighting Vehicles in my platoon. We didn't get attacked unless someone was looking for a big fight. The units that did the daily logistic convoys (which women were assigned to) were much softer targets given the type of vehicles those convoys were comprised of. Also women were assign to military police units. Some MP units were doing route clearance missions just like I did from time to time. Women, quite obviously, faced "real" combat in Iraq too.