Here is a book you should check out. It was originally written for law enforcement but the info is pertinent to firefighters. It will help you understand what she is going through and give you some ideas on how to handle it.
Emotional survival for law enforcement: A guide for officers and their families https://smile.amazon.com/dp/0971725403/ref=cm_sw_r_apan_glt_fabc_0RGM10PJB7DAYMW8GQHD
I was a firefighter for 24 years. Received a medical retirement for PTSD. Hopefully, her department has peer support for days like this.
Also, the responses by the others here are pretty spot on.
Amazon sells a bunch of them Rite in the Rain Weatherproof Top-Spiral Notebook, 3" x 5", Black Cover, Universal Pattern, 3 Pack (No. 735-3) https://www.amazon.com/dp/B01N0139W7/ref=cm_sw_r_cp_api_i_1kyEDbJ4N1S0H
I recently purchased this Schrade along with a tek-lok and clip it to my radio strap. I love it and have actually purchased it for friends as gifts.
Schrade : Schrade SCHF57 Full Tang Fixed Blade Knife https://www.amazon.com/dp/B019RSXPEI/ref=cm_sw_r_cp_apa_v1zrAbKWZ59XX
Tek-lok : Blade-Tech Tek-Lok with Hardware (1 - Pack) https://www.amazon.com/dp/B00G2DPHFM/ref=cm_sw_r_cp_apa_sYzrAbG0B40C9
In our state its blue and white only (NY). I've been told off the record that you can't have them until you pass Firefighter I but I jumped the gun a bit and This cheap set on Amazon which are fine. (I was told the day after I fitted them - guess I won't be using them for a bit)
We also need a permit from our chief to run them in case we get stopped by the cops.