Speak your truth. From how it reads to me, your truth is something like:
"Thank you for asking me. Right now I am feeling uncomfortable with the idea of Denise and Tyler pursuing an independent relationship. I'm still processing all the feelings that were brought up from our hanging in trio so I'm not sure how much I can digest at once.
I am willing to discuss/explore why that is with you two at this time. / I am not willing to explore/discuss why that is with you two at this time because I need more solo process time. "
This is being honest.
Your worry of being seen as hypocritical or controlling?
Deal with that one when you get there. Cuz that's not your bag -- you are owning your own baggage by reporting your internal emotional weather. If this causes other people weather, THEY have to report their own shit.
Emotional intimacy is emotional intimacy. Sooner or later you get around to sharing the Vulnerable feelings. Some of that emotional weather is like sunny days, some of it is like cloudy, some of it is like stormy.
I'll quote Tyler:
I kinda like the sound of him actually, if he means it truly and not like flippantly. "It is what it is, we deal with it" has a big appeal to me.
We feel what we feel when we feel it. We do not get to choose that.
We only get to choose how we behave in response -- react or act with intent.