If she wasn't fully dilated, then really it seems more an issue of FTP (failure to progress) than CPD. Both issues are often bogus, to throw my opinion out there.
Here it would depend. As long as the baby was looking good, if the mother wanted to keep laboring, she would have been "allowed". If the mother had been pushing for a c/s most of our docs would have taken her back in a shorter period of time.
A quick FYI-unless this woman had an IUPC, the mmHg on the toco doesn't mean much. I've seen women get Braxton Hicks up to 90, and women deliver a full termer while only registering in the 40s on the toco. I can't tell you how many times I've answered a call bell from a family member (or the woman herself!) "OMG! Come quick! She (I) just had a huge Ctx!!" so I go in, ask the usual questions (LOF, VB, mucus plug, etc). I ask how painful it was and I get "Oh, I didn't even hardly feel it. But you shoulda seen those numbers moving up!"
Placement of the toco, position of the baby and uterus, body shape, body mass index, etc can all effect the readings. An external toco is really very relative.
Burn out-Not trying to sound snarky, but a primip opting for a c/s after laboring for 12 hours (am I correct that labor was 12 hours and SROM was 20?) is far from being one of the hardest times here. Far far far, especially when mama and baby are alive and healthy in the end.