Not enough is said about how Porsha played Phaedra. Porsha knew she lied, and knew Phaedra was going to sit back and let her suffer by herself for it.
I knew the whole time the lie came from Phaedra. I also recall that Porsha was on WWHL just prior to the reunion. She got TONS of backlash for the situation yet refused to give up her source. Phaedra was at WWHL with her in the audience, probably thinking she was coaching her so she wouldn't spill the beans.

The whole time, Porsha knew she had to throw Phaedra under the bus to save her own peach. So she didn't do it on social media or on WWHL. She waited until the opportune moment: the reunion. She threw some tears in it and made the moment very dramatic, caught Fraud off guard and left no time for her to recover because the season was over, ensuring that Fraud would take the downfall herself.
How very Cersei of her.
"I'm going to let Phaedra tell you since she is the one who told me."
Phaedra: 