no advice re the f act that she is SN, but if you want a NT child viewpoint I can add mine in.
I have a 13yr DD and a nearly 12yo DD.
while in yr 6 & 7 they both really suffered from monthly tummy pains, to the point of tears should they still get sent to school. interestingly in was also at the same time as my periods......and I suffer from evil pain.
to start with I did wonder if it was attention/school avoidence/social school side issues etc, but after a chat with my HV (I had a fab one then), it seems that it is common with many girls of this age.
their bodies are readying them for puberty and periods etc, and their wombs are developing (as are their overies), for the monthly hormonal onslaught.......and it does cause pain. it doesn't neccesserily mean tho that they will have pain when they do get their periods tho.....just that their bodies/tummies hurt now.
in fact, for my girlies, it all settled down within 10/12mths and now both are not bothered.......may mantion the odd ache, but not the tearful pains they got before (and as yet, neither still have yet started their periods!).
I just gave them sympathy and the odd day off with plenty of painkiller (ie....calpol), and when they saw that I would take it all seriously they seemed happy to carry on when hurty.
I know your DD is SN, so it may be different in the way you want to deal with her......but don't automatically assume it is for attention/skiving.......she may indeed just be developing and hurty and scared. mine were.
HTH