When my kids were small, but old enough to understand, I told them that if something was happening at our house that made them want to run away, please go to a friend's house that was safe, and we'd work everything out from there. In high school my daughter reminded me of that and asked if it worked in reverse - could a friend who felt the need to leave come to our house? Yes! That is essential, to keep them safe. The friend who might have come over never did; it may have been enough to know that another family could support her if she needed it.

That said, I wonder if your friend would like some time away, to go over to your house for a sleepover visit? Or find an excuse for a brief road trip in the area to give them breathing space and her a chance to share if so inclined?

Relationship trauma can happen at any age. Is theirs a relationship of long-standing (and the trouble may be due to dementia, etc.) or a new relationship? That might make a difference.