It happened to me. PMB is always treated urgently, so I was seen within 2 weeks. It turned out that it was due to age-related thinning and fragility of the epithelium. I was told that this, along with benign polyps, is the most common cause of spotting after the menopause. I hope the same will apply to your daughter.
I'm post menopausal and bled heavily after being put on Hrt, eventually got that under control with Northisterone 5mg 3 times a day and still need to take it now or would still bleed. After extensive testing mine is diagnosed as dysfunctional uterine bleeding. In other words they can't find an explanation for it. I'll be on the tablets for life which is frankly better than the alternative. Don't worry until you have something to worry about.
Similar thing happened to me FlexibleFriend I eventually persuaded my GP to let me try HRT to stop the debilitating hot sweats (night and day) but I began bleeding quite heavily. Eventually saw a consultant and had various biopsies done. Thankfully all okay. I was also given Northisterone to stop the bleeding which worked well but caused terrible bloating. At 58 I am now back with the awful night sweats and day time hot flashes too.
I am wondering if your DD has recently started HRT Anniebach ?