Hahahahaha! She really dug her own grave this time. She's a freakin' idiot. Not even considering the implications of extended family in her scheme and then blatantly lying to her "father-in-law" without a second thought. What a freakin' moron.
"Oh, congrats on your son's upcoming marriage."
The father's just there thinking, "What?". Bet he's probably though that his son met this girl but never decided to introduce her or anything and is wanting to cut ties with how quiet he's been.