Short version: that time of the month hit as we were doing the deed and that was the end of the session,  No offer to finish thing another way or reschedule or anything.  I left poorer and unsatisfied.  I was pissed but wasn't going to risk that she might make a scene,

It's quite possible it was just a piece of bad timing (things had been going well up until that point) compounded by her being new and not even thinking she should make an attempt to set things right but then again maybe not.  

In any event, thought the rest of you should know.  Review to follow when I have time.