@SarahAndQuack
Did you not see earlier episodes when Sister J was very definitely shocked about the idea of providing contraception advice?
Obviously she had seen thousands of unmarried mothers, illegitimate children, and botched home abortions.
Her reaction to tampons in the hallway isn't anything to do with being an innocent shrinking violet. It's clearly coming from the same place as her reaction to contraception talks - she wouldn't think Nonnatus House was the place for it and I suspect she wouldn't approve of unmarried women using tampons.
It's really not that long ago people considered tampons quite inappropriate for unmarried women (because it was thought it might damage the hymen). My cousin was an Anglican nun; she's not still with us so I can't ask her what she'd have thought, but I'd be gobsmacked if she'd have thought tampons were acceptable.
I don't think these things are particularly similar in the end.
While young girls might not have been wearing tampons much in 1967, it wasn't that unusual for older women to do so. And an Anglican nun with a good education would not likely have thought it would impinge on someone's virginity.
Contraception on the other hand was still seen as a moral issue in an entirely different way, and when Lambeth discussed the issue in the early 20th century their decision was that contraception could be used by married couple with serious reasons but would have detrimental social effects if widely distributed, and they felt that even that decision might be questionable. In fact that episode somewhat hints at some of those things in what Sister J says though I thought at the time it might have been quite interesting to explore it further, as some of the things they predicted did in fact come to pass.
But in any case, it was a real religious problem for Sister J in a way that tampons simply never would have been.