The person I dated made out with someone else in front of me. What should I do now?

utual friends, including another gay girl, let's call her M. Now both of them knew that I liked J. I took J on some romantic dates. Took her to Santa Barbra, picked off flowers for her as we were walking, paid for a romantic dinner at an Italian restaurant there. When we came back, we cuddled, kissed, n made out. After that date, she started getting "busier." Basically, we haven't really hung out much since then only a couple times and it felt pretty casual like she thought of me as a friend. She knew I liked her. The other girl, M, knew I liked her. Yesterday, we all went to a club for my friends birthday. I brought my friend from work along (she dressed really nicely. great skirt,etc. She looked hot). And it was weird because our mutual friend, M, comes up to my friend and asks her, "Hey so are you two going out? What's your ual orientation? Are you two together?" My friend told her no we're just friends and she's bi. And then M, with her big f*cking mouth decides to make it known to everyone and blurts it out. Esp. to J! And she especially makes it clear that my friend is and whispers to J that makes her look at me weird. During this whole time, I can see J coming closer to me. Like she was watching my interactions with my friend. Possibly jealous. Next thing I know, I see J, the girl I liked and cared for, flirting with multiple people. Now flirting isn't really hurting, so I kept my cool. I got angry when M AND J STARTED MAKING OUT LESS THAN 5 FEET AWAY FROM ME, FLAUNTING IT IN FRONT OF MY FACE. I WAS INCREDIBLY ANGRY. SO MUCH, I WANTED TO PUNCH BOTH OF THEM HARD IN THE FACE. But I have self-control, and I'm a cly person, so I didn't. But what should I do now? Let it go, right, obviously. But should I confront J today and be like "hey i liked you. We went out on dates and stuff and I showed you care an affection. You made out with M yesterday and flaunted it in front of my face. You just blew it. Have a nice life."? I feel like I want to confront her and her stupid actions. But do you think that will be effective? What should I do now? :(