I don't know if its just a "woman thing" or not. Like you said, I've known some male instructors were saints, and some female instructors who really don't want to bother with the students. I think it is a personality thing too. I'm a nurse, a "caregiver", by profession so I think thats that what I do best.
As for problems students: We once had one of the sale people at the dive shop that was told she had to get certified so she would be able to know what she sold. (Why they didn't find out if she dove or not before they hired her I'll never know) But turns out she didn't swim well and really didn't want to dive, but she wanted to keep her job so she agreed to take the classes. She did nothing but complain and belly-ache the whole time we did pool. And then there was open-water .... All kinds of excuses why she shouldn't/couldn't make a dive ... "It's too cold." "My wetsuit doesn't fit well." etc, etc. She totally "excused" herself out of one weekend of open water and was working on a second. We finally got her into the water and over to the dive buoy and then every time Don tried to take her down the line to the platform, she couldn't clear. I still don't know why she just didn't say forget, I quit but she didn't/wouldn't. So finally Don turned to me and says "You take her down the line, I don't care how long it takes." It took 45 minutes to go down 30 feet of line. But we got down and Don did her skills and she did fine. Until the next open water dive. Then we did it all again. By the time the weekend was over, I was about to pop but we got her certified and she still works at the dive shop. She talks like a pro but I don't think she's made another dive since she was certified.