Asacol has never caused me any pain.
If she she has inflammation in her colon which is what UC is then that will cause pain. UC is ulcers throughout all or part of the colon. I just imagine if my mouth was full of ulcers it would be pretty sore and the same goes for your colon it gives you stomach pain.
Inflammation causes the colon to go into spasm which causes the stomach cramps. When I am flaring this happens intermittantly thoughout the day but I am also left with a dull ache pretty much all day. Hot baths or hot water bottles definately help this. I am sure that once the inflammation is under control the stomach pain will go. But if you are worried that she is having a reaction to the Asacol you should speak to your doctor about it.