Oh FFS why are people being so unkind? Questioning the OP like she's making this up....! There are mothers in this world who have very little or no maternal instincts with their children and will be very emotionally abusive and neglectful - why is that so hard to accept.
And questioning why didn't the OP just ask this or do so and so?!
Because when you have been raised by a narcissist you are TRAINED from birth not to question, not to think for yourself, not to show initiative or take action for your own needs. You're trained not to think that you even have needs. So no, it wouldn't occur to an abused hold just to "ask" or to "get some from the school nurse" or whatever...!
OP have you ever looked at this website? I found it very useful 
www.daughtersofnarcissisticmothers.com/
My own DM was always weird and awkward about these things. She claims she was always very open and honest because that is how she likes to think of herself. The reality is that she didn't tell me a thing and I remember learning about periods at Y6 sex education when I was 11. I remember feeling utterly horrified and terrified at prospect and thought "why has no one ever mentioned this before?!"
When I got my period I looked down and saw the blood in my underwear whilst on the toilet. My mum was in the room (no privacy) and I said something like "oh my god look!" because I was so shocked. My mum came over and looked. She sighed a huge sigh of disappointment and said "well, looks like you've got your period then" then walked out the room, leaving me feeling like I'd done something wrong.
She made a big song and dance about buying me pads and kept buying me different ones to the ones I'd asked for (I wrote it down for when she went shopping - I think she did it on purpose). Then used to make me bring my pads home from school so she could look at them before putting them in the bin.
I also suffered with horrendous pains and heavy periods back then and was practically incapacitated with pain. She told me "I hope you don't think you can miss school every month" and sent me in, despite the fact that my friends regularly had to drag me to the nurses office because I was passing out and I spent many a missed lesson lying in agony on the nurses bed.
Fun times 
Oh and she also used to make me wait ages for pain relief or a hot water bottle. She'd leave me lying on my bed and say she would go and get me one. Half a hour later I'd drag myself downstairs to see where it was and she'd be cleaning the kitchen or something