I don't get the impression that Lynn was deadset choosing Maura at the time she was cheering her on. Lynn was engrossed in the spectacle of the panty wrestling. I can see how you are interpreting Lynn's cheer, and agree it is a little ambiguous. But I still get the impression that Lynn wouldn't have denied Didi some sexi-times should Didi have defeated Maura. To the victor go the spoils.
As far as Maura's confused interest in Lynn: I think she is just that... unsure of herself and competitively desperate. Lynn has been pouring the charm on pretty thick. And, Maura is privy to knowing that Lynn is sexually interested in Didi. Didi is not privy to the knowledge that Lynn has also been flirting with Maura. I suspect that Maura does not want to lose her 'relationship' with Lynn so much that she'd be willing to do just about anything - including sleep with her - to keep her #1 in Lynn's eyes. A wrestling match? No sweat! Maura has no problems laying some moves down to defeat Didi.
Once the adrenalin ends though, will she be so keen to get more than just a kiss from Prince Charming? If she goes through with it, will she have regrets? All of this is beside the inclusion of Lynn's kink.