I actually liked the scene, and in my opinion it made sense given Ivy's personality: she's a total sub and Renee comes along and pushes her to take that first step.
But because Renee is a deplorable pervert, she interjects herself into the situation because she wants some fun too.
Honestly, the only thing I would have changed is to have MC lean over and whisper into Ivy's ear "The safe word is pineapple. You say that, and we stop, no hard feelings". I think something like that would show that MC is okay being a very dominant lover, that Ivy is totally okay with being a bottom buttslut, and that Ivy (not MC, not Renee) was the one truly in charge of that situation.
For me, the explicit consent to be treated like a sex toy is the hottest aspect: Ivy desperately wants what's happening, and Renee and MC can see it, but they know she's too shy to ask for it so they take what they want with Ivy having the safety of knowing she can shut it all down.
That would have been the chef's kiss.