Periods are just hard and one of the psychologically logical reactions is denial.
Back in time, I totally refused to record my periods and if someone had came with big calendar as PP suggested, it would have alienated me even further. My mum hadn't provided me with painkillers (originally), so she knew when I was feeling really poorly and needed to go home from school in the middle of the day. When she reminded me to keep records and mentioned she remembered the dates so far, I felt totally betrayed. She was denying me my denial!
I had troubles with hygiene for some time, because in my denial I haven't noticed the physics - if my underwear was too loose, the pad wasn't safely in place. No period pants were available back in time, I suppose they help a lot.
I was looking for ways to get rid of periods, but I loved food, so I hadn't managed to get underweight enough. At one moment I was eating some random green leafs and hoping it would magic it away.
And yes, I hated all words standardly used for periods, too much focus on "this will happen again and again" and no appreciation of "I don't want it".
I don't have much advice. Thinking back about what would had help anyone communicating with me... I'd say acknowledge she doesn't like it, maybe establish some home code (very brief and kind of indirect) *. Don't push it as "ok" or "normal" - yes it is, but it is normal to hate it. Focus on the managing part - is she in pain? Other kind of discomfort? Can you help her to manage it in very, even insanely discreet way (I hated going to the main bin with packed used pad after having my evening shower. It felt way toooo obvious, but in my culture there were no bathroom bins and honestly, I'd had been scared anyone can look into them/notice when throwing them away).
Sounds you tried a lot to support her, so maybe this is just an encouragement that someone would had appreciated your approach :)
*I know that denial doesn't really help and using proper words is important, but she will have enough time for that.
PS sorry about grammar, I don't get to use unreal past conditionals much, so this part of my English is a bit rough.