I'm no aviation expert, but I would have thought the pilot had a lot to answer for:
1 If (as I suspect) the suction is generated by the difference in air pressure between the toilet and the tank into which the toilet empties (which is presumably in the unpressurised hold), then why did the pilot not reduce altitude and equalise the pressures?
2 What, in fact, was the reaction of the pilot when he heard of the woman in the toilet? What action, if any, did he take?
3 Did the pilot have a reason, currently unknown to us, to restrain the woman on the toilet seat? Was she a violent person, or had she made threats to hijack the aircraft?
I'm sure we haven't heard the end of this.