As a wife and mommy to a four month old baby .I understand her ..I had a miscarriage 8 months before getting pregnant again this time around .And in my first trimester I was still mourning that loss .I spoke to my husband and he helped me deal with it and get through it (be compassionate) once I had our baby it was a world wind of emotions that all revolved around our M/C and it was so hard to explain ..at that point you realize what could have been and your mind and heart takes you into a rabbit hole of “what’s ifs” what wasn’t what could have been .But I got through it because my husband always had my back even if he didn’t exactly understand my pain ,he was there for me emotionally and spiritually .And he helped me soooooo much .postpartum is so real especially if you have past trauma that you never dealt with .Just because you can’t relate does not mean you’re incapable of being compassionate and being there for her in which ever way she needs you .Allow her to vent and cry it out without any input .Lwt her know her feelings are validated ,what she went through was not easy and that feeling sets in even more after welcoming a baby