Hope this helps
All I can do to help is tell you how we worked it out.
My wife and I agreed when either of us schedule time with our GF, the other usually keeps it quiet on the texting. We also agreed that when its me and just the wife, neither of us is to text with the GF just so it can be us time.
I actually felt the same way for a long time, our GF was the wifes GF first. I talked it out with them and we agreed what we would want as per us time. Other wise, they chat while we're in bed and we all say good morning, and goodnight everyday.
It made all of our relationships stronger talking it out, we didn't set limitations, just understanding, kinda like in the sense, I wouldn't text my best friend while on a date with the wife, it would be rude.