Yes/Chad/Convince Gwen to stay before she takes off
You can't have her running off, and that's just what she'll do once the shock wears off if you don't intercede.
"Gwen, would you please have a seat so we can talk?" you ask. At her name, you mom instantly springs into high alert mode.
"Okaaay," says Gwen as she grudgingly sits in a chair across from you.
"Gwen!" says your mom as she tries to put herself in order without clothing and with your cum running down her leg, "this isn't what it looks like. I can explain. I-"
"Mom, could you go wait in the bedroom? I'll talk to Gwen."
"Yes, Of course." She starts to leave, but you pull her into a kiss before she can go just to drive the point home to both of them how things stand. She blushes, and disappears upstairs . . . which leads to the question of whether she's going to her bedroom or yours, but you can sort that out later.
"You're fucking mom?" asks Gwen rhetorically, disgust evident in her expression. "I guess nothing is sacred, you perverted poser."
"I'm sorry Gwen," you say somberly. "Does that make you jealous?"
The power marks her face and she says, "Yes- I mean NO! Why would I be jealous?"
"You wanted to be the one I was fucking instead of mom, didn't you?"
"Yes- damnit . . . NO! What's going on here."
"Could you calm down so we can talk rationally?"
"Fine," she says with a huff. She seems conflicted. It makes sense, you suddenly made her jealous of your mother, and desirous of sex with you while she is still rebellious of your authority over her and to society at large. It's a lot to process in an already hormonal teenage brain.
"Look, just because I'm dating mom doesn't mean I won't have time to spend it with you . . . if you want. Would you like to spend time with me?"
"Yes . . . I mean, no, your my poser brother. Why would I want you to fuck me? You're just trying to make an incest harem. Have you gotten Emily? What about Bree, you perverted freak?"
"I haven't touched Emily or Bree sexually," you say. It's technically true, but you have thought about it. "Is the thought of me fucking everyone on the family turning you on?"
"Yeah . . . GOD! Am I a pervert too? Did you just make me into a pervert?" She seems on the verge of tears. Maybe you went too far . . . or maybe not far enough.
What route do you take?