Only because there has been some previous discussion in this thread about how one's age, sex and sexual orientation might possible impact one's view of the subject matter, by way of background I'm a straight male senior citizen who has never read Pygmalion. I saw this production last night and will confine my thoughts to to its ending (though in short I thought the entire thing wonderful.) And I'm also the kind of guy that cries at RomCom movies. In other words, I too love happy endings.
I knew going in that there had been much written about the ending but I avoided reading anything about it as I wanted to experience it for myself, not knowing how it "came out." So as I was sitting there during the last scene, I was saying to myself, "Don't go back to him Eliza, don't do it." I did not think this because I thought Higgins to be any type of monster, as I didn't. He was who he was, a man pretty much set in his ways, as confirmed by both his mother and by his "Now where the devil are my slippers?" final line.
But my hope was based on the simple fact that Higgins thought of Eliza as his "possession", as in someone whom he had created, and as such, believed in his heart that she would and should always be submissive to him. What he failed to understand, in my view, that Eliza was someone in whom he had created self-respect. And that was how I hoped Eliza would view the situation as well, and it turned out that she did. She knew, in her heart, that if she stayed with Higgins she'd always be, in his eyes, a guttersnipe that he had "cleaned up" and made presentable, but that she was someone who would never have Higgins' respect.
I don't think she ran back to Freddie, because just as Higgins did not have respect for her, she did not respect Freddie enough to want to spend her life with him. Sure, she had feelings of affection for him, but she saw herself, finally, as someone who deserved more out of life. And so, it was, to me, a happy ending after all because I felt she'd have the life she deserved.
CZJ at opening night party for A Little Night Music, Dec 13, 2009.