Here's the thing, babe. There has always been an asymmetry in our relationship. One of us (you) has been more invested than the other (me). As much as I try to be a committed girlfriend, I simply cannot stop thinking of what I had in the past (him). I know you try so hard to be the best boyfriend, but you'll never be able to keep me sexually satisfied like he can. His cock is PERFECT. Literally, perfect. Life changing. He fucks me so good that I forget my own name. But you.... ehhhh. I'm so unsatisfied with your size and performance that I can't even fake pleasure. How pathetic. I need way more than what you can give, I need to get dicked down by a real man. An alpha male.
I know it's humiliating to hear the truth, but I have a solution for our little problem. It involves me bouncing on his dick and you, kneeling, watching, and waiting patiently to have your throat filled with him.
Don't bother resisting - it only signals to me how much you want this. Being my cuckold boyfriend is better than not being my boyfriend at all, right?