Pre Teen Daughter Hygiene.

Hello, needing some advice. How can I approach this issue in a way that I haven’t already?

I am a mum of a 12 year old daughter who is not handling menstrual hygiene appropriately. Although she has not started her periods yet, she is wearing liners to keep herself feeling clean during the day/nights. The problem is the lack of disposal. I’m talking about stuffing 30+ used liners into her cupboard, sticking them to the bathroom bench etc. We have bins in all rooms of the house, which she has access to, I have also supplied sanitary bags for privacy if that is what she is needing. Ive had multiple conversations with her, written her letters about how important female hygiene is and how easy it is to dispose of these correctly. We share our home with other family members too who are also coming across these just laying around everywhere. It doesn’t seem to be an embarrassment issue with the fact she literally leaves them stuck to benches, middle of the floor etc. It also doesn’t seem to be a mental health issue.

I’m at my wits end and I’m approaching it in such a gentle way as I know becoming a teenager and changing bodies can be a tough time but the laziness and lack of hygiene is beyond a joke now.