21.—(1) It shall not be lawful for any person to be a member of an unlawful organisation.
Unlawful organisation according to who though?
According to the UN perhaps but if it's just according to Ireland then mightn't that adversely affect our neutral status if we as a nation are proscribing organisations in other countries?
"Oooh there's a crowd out in Myanmar and I don't like the cut of their jib. Let's proscribe them so that if any Irish citizen is found guilty of being a member then we can do him/her under 21.-(1)". Not sure how that would work tbh.
BTW ISIS were a shower of scumbags imho but I'm just trying to tease out what IRISH law she definitely broke by becoming a member, and she might even suggest a coerced in fear of her life member.