At the end of Cloud 9, Betty is sitting on a park bench. Clive (who's been MIA since Act 1) shows up and tells Betty that she's "not that sort of woman" (2.4.273), meaning that Betty is not the sort of woman who can live by herself and pick up men in the park.
Betty doesn't answer, so Clive rambles on about how he'll never be able to love Betty the way he once did. He's actually repeating what he said in Act 1 when he found out Betty had kissed his friend Harry. What Clive doesn't seem to understand, though, is that the world has moved on and that he can't get away with being a sexist patriarch anymore. Clive says a few more things about how he "used to be proud to be British" (2.4.275-276), which sounds kind of nice until you realize that for him being British is synonymous with getting to be a sexist and colonialist.
At the end of the play, Betty is finally able to let go of Clive and everything he stands for. She accepts herself as an individual, and Caryl Churchill symbolizes this by having Betty from Act 1 (played by a man) come onto the stage and hug Betty from Act 2.
Betty from Act 1 only ever knew how to make men happy, but Betty from Act 2 has finally learned to live life on her own terms. It's a great triumph for Betty to finally leave Clive and all his sexism behind. In her old age she's finally come into her own.