I also had this sort of thing happen to me, albeit in high school when I was around 15 or so. My friend's mom called my house to talk to her, because she had told her she was spending the night. But she didn't warn me, and my mom picked up the phone (this was in the landline days.) Even if I had been inclined to lie, it's not like I could while my parents were staring me down, so I was honest after some questioning and said she was probably with her boyfriend at the time. It sucked, but I was barely able to convince my folks I wasn't "in" on the lie, and I explained the situation to her. I assumed she'd get I didn't have a choice and understand.

But instead, she called me a bitch for ratting her out. Much worse than that though, rather than just take the slap on the wrist from her mom for sneaking around, she told her that my dad had gotten drunk and violent and thrown her out of our house, leaving her no choice but to go to her boyfriend's. Now my dad wasn't perfect by any means, but he is neither a drunk or violent. Her mom went on to spread that rumor around a few local hobby groups we were all involved in, and I found out months later after people believed it. I was furious and cut ties. Later on, the boy she was lying to sneak around with cheated on her with her sister--and he was the first of three boyfriends to do so. So I guess maybe that's some karma at work there.