You do not need to understand every part of period pain to be a good partner. The first act of care is smaller and harder than finding an answer. It is making room for her account of her own body.
Begin with belief, not investigation
When someone says a period is making her miss work, lose sleep, cancel plans, or change how she moves through the day, listen to the cost she is naming. Pain can be invisible while its effect on a life is unmistakable.
Try: “I believe you. What has this been changing for you?” That sentence does not assume a cause. It tells her she does not have to spend the conversation convincing you that the experience is real.
Do not turn concern into an interview
Questions can help, but too many can feel like doubt. “Are you sure?”, “How bad is it really?”, and “Was last month not okay?” can make her defend a story she is still trying to understand herself.
Ask one useful question at a time. “Do you want me to listen, help with something practical, or think through the next step with you?” gives her control over the kind of support she receives.
Let uncertainty stay uncertain
She may not know why this is happening. She may not remember exactly when it changed. She may feel certain one day and doubtful the next. None of this makes the experience less worthy of attention.
Resist searching for a diagnosis in every detail. A partner can help preserve the facts without turning them into a conclusion: what changed, what she missed, what she tried, and what happened afterward.
Keep the door open after the hard day passes
The next morning may look ordinary again. That is when important things often disappear. A quiet follow-up can help: “Yesterday seemed difficult. Do you want to keep anything from it for later?”
If she says no, let the answer be no. Support is not surveillance. Your job is not to monitor her body. It is to make it easier for something that matters to be remembered when she wants to return to it.