Hi and welcome to r/AskHistorians! I really hope someone here will be able to point you in the right direction. In the meantime, both as a military historian and as a moderator of this sub, I just want to say that this is a fantastic project and I really hope you will pursue it as far as you can.

I personally work on Classical Greek warfare, and because of a couple of malleable passages in Greek literature, there is an ongoing controversy in my field about the question of ancient PTSD. However, this discussion always focuses exclusively on male citizen warriors, and never even considers the experiences of ancient women. While this focus is driven to some extent by the available source material, it is a terrible oversight that leads to the stigmatising and unhelpful perception that PTSD occurs only in or because of war.

On this sub, we get a lot of questions about PTSD - but these, too, invariably focus on the experiences of soldiers. Questions about ancient PTSD are common enough for us to have a section in the FAQ about it. There are also frequent questions related to the trauma suffered by soldiers in 20th century conflicts. However, there has never been, to my knowledge, any question that considers the occurrence of PTSD among women or civilians. This is exactly why the focus of scholars in my own field is so harmful. It reinforces the apparently widely shared perception that PTSD exists only in a military context, and affects only adult men. People just don't seem to wonder about PTSD as the result of other traumatic experiences (sexual or other physical violence, abuse, crime, accidents, etc.). They ask neither about its history nor its treatment. The voices and experiences of women and non-combatants are lost.

Your question, then, is absolutely brilliant and necessary and deserves to be studied in depth. I really hope you'll find what you need here, or that at least you will get the pointers you need in order to continue your research. Best of luck!

As /u/iphikrates said, this is indeed a great question, and I definitely encourage you to research it further. I have written about 'shell-shock' here in the past. I want to check whether you're specifically looking for British women and/or specifically looking at the manifestations of mental illness in World War I that are most commonly called 'shell shock'?

But in general, I would argue that there was a very heavy genderedness to psychological diagnoses of the period, and that it's very likely that women with symptoms like 'shell shock' which result from exposure to trauma related to World War I would have been diagnosed with 'hysteria' rather than 'shell shock'. So if you're doing your own research here, I'd broaden your search terms to look for 'hysteria' as well (especially as 'shell shock' was generally seen as a fairly uncertain diagnosis that caused a lot of furrowed brows - doctors weren't quite sure what to make of it, or what it was exactly, and it probably seemed rude to accuse soldiers of having a female condition like hysteria).

It's also worth pointing out that World War I was well before the modern era of very carefully delineated disorders such as you might see in modern editions of the ICD or DSM (manuals used for diagnoses of mental health used internationally, and amongst American psychiatrists and psychologists respectively). And speaking of which, shell-shock-like symptoms would have been called 'gross stress reactions' in the 1952 edition of the DSM, 'transient situational disturbances' in the 1968 second edition, and 'post traumatic stress disorder' from the 1980 third edition onwards (British psychiatrists diagnosing such symptoms would likely have used the ICD rather than the DSM however, but often the diagnoses are broadly similar in each).

Additionally, if you want to look broader than British women and WWI, I have found a psychological research study on post-traumatic stress in female miltary nurses in Vietnam and some research based on recollections of female Australian military nurses who served in World War II and in Vietnam.

Finally, there is a very interesting 2014 article in The Atlantic by Hannah Groch-Begley on pretty much exactly this topic, which may well be based on parts of a thesis, as googling suggests that author is now researching a history PhD.