I think the line is being muddled between comediennes and comedy actresses. I wouldn't call the likes of Joanna Lumley, Tracey Ullman or Caroline Quentin for example comediennes, funny though they might be when acting. Someone has even mentioned my absolute favourite Bette Midler whom we went to see in Vegas 18 months ago. But she is first and foremost a singer who will talk about her friend Sophie in a funny way and a comedy actress.
For a stand-up comedienne my vote also goes to Victoria Wood.