Adding on to BonBon's comment about Emma's relationship with her mum, Nannysan. I concur. It's very obvious that San is the type of woman who sweeps things under the rug. I'm ten years older than Emma, & it was a sort of competition between my friends and I about who started their periods first. I was last, quite late at 15, & my mum reassured me that she was a late starter too, what to expect, would I like to try tampons, etc., ... this was circa 1979-1983 and was most certainly NOT "taboo"! Same for the peri/menopause, my mum talked to me about her journey and what to expect when my time came (it's been & gone, 19 months menopausal, on HRT patches). The way she is giddy over the phrases "up your bum" & "shove it up my/your bum", calling sex "private parts action", & clamouring for attention from deviants online, proves that she truly is a product of her environment and that San raised her daughters to be ignorant and sheltered. Hence, making lovey-dovey sticker photo scrapbooks at age 30 and being into boy bands and The Spice Girls in her twenties. She's raising Erin in exactly the same way. Chaperoning her on shopping trips, Clifford The Big Red Dog at the (chaperoned) cinema. No talk of her being open with Erin about periods, sex, menopause etc., .... the cycle continues.
In conclusion Emma, none of those topics are "taboo", your mum just did a shit job. We don't live in Gilead.