Gwen , in other families most adults have the wit to realise that if a teenage girl complains of abdominal cramps that it's likely to be due to them having a period, without the poor girl having to provide detailed reasons/ diagrams/ evidence. It's not a welcoming environment if girls are forced to disclose details about their bodies that they are not comfortable with sharing.
There are two issues here.
One is that cultural expectations in many societies bring an element of shame to women's biology, with menstruating/post-partum girls and women being shunned, or forced to live in dangerous conditions, or with their sanitary needs not provided for, or with the pain and complications of genuine medical conditions being dismissed as 'just women's problems'. Clearly this situation is wrong, and it's absolutely desperate for those women and babies pushed out to live in cowsheds after giving birth because they are considered 'unclean', or the women and girls at risk of rape and murder in remote locations because they are forced out of their homes while menstruating. Nosey grannies demanding personal information isn't going to help these women one jot.
Even in the UK, the growing demands from some MRAs/TRAs to decouple the rights of women from the legal protections available in respect of their biology drive women's medical and reproductive rights further into the background. Likewise, politicians legislate over women's bodies, with women criminalised in some countries for suffering a stillbirth or miscarriage. In the US, politicians force through anti-abortion legislation while pressuring their own wives and mistresses to have abortions themselves. Religious and political leaders- the vast majority of whom are men- are dictating how society must treat women and their reproductive health, and using threats and violence against women who don't comply. Somehow, as women, we need to fight against this with a unified voice.
However, the drive to improve attitudes to women's health DOES NOT compel any woman or girl to give up her rights to medical privacy. The second issue, which is obviously closely linked to the first, is that women and girls do (in the UK at least) have the right to bodily autonomy. That means that the OP doesn't have the right to share the OP's information with just any person who asks (obviously circumstances which involve the need for health care professionals may arise and need to be addressed in a particular way).
The way to improve attitudes to menstruation isn't to force 11-year-olds to publicly declare what's going on with their bodies if they choose not to. It's bigger than that.