My mom is pissed about what my friend and I did last weekend

Okay, so my friend (F/16) and I (F/16) were having a sleepover at her place. I arrived on Saturday around noon. After a couple hours of goofing around, we decided to raid her older brother's room in search of a DVD we wanted to watch that night. We found it, but not before we noticed the pair of handcuffs he had left lying on top of his dresser.

My friend picked them up and, long story short, we jokingly handcuffed ourselves together, my right hand to her left. And then, a few minutes later, we realized that what we thought was the key to the cuffs was actually the key to a jewelry box that was also on the dresser.

Her brother was out of town, so we called him to explain our situation and ask where the key was. He laughed and said it was with him and that he wouldn't be able to return until the next day.

We weighed our options. We could either cut them off or call for a locksmith. Neither of us wanted to destroy her brother's cuffs, since it was our own fault we hadn't tested the key first. And neither of us wanted to put our plans on hold to wait for a locksmith. Thinking it might be kind of fun to spend the night handcuffed together, we decided to own our bone-headed move and explained the situation to her parents, along with our decision to stay cuffed to each other until her brother returned. They got a good laugh out of that, but agreed to let us do it.

So, we carried on with our plans and didn't let the fact that we were stuck together stand in the way of our having fun. Her parents took us bowling (which was definitely a challenge!) and then to a movie. We got a couple of weird stares here and there, but we didn't care. After all that, we went back to her place and stayed up late watching scary movies. We eventually went to sleep on the bottom bunk of her bunk bed. Originally, the plan had been for me to sleep on the top bunk, but that was now out of the question, lol! So we had to squeeze onto one bunk. It was a tight fit for sure, but we made it work.

Her brother returned maybe an hour before noon on Sunday and we were finally freed after spending nearly twenty-four hours as conjoined twins. It had definitely been a challenge, but fun too. We told our friends about it at school on Monday and they all thought it was hilarious.

The only person not laughing was my mom. She found out about it yesterday and was livid. She says I'm no longer allowed to sleep over with my friend. She says it was really irresponsible and unsafe for us to spend almost twenty-four hours like that and that her parents should've never allowed it.

WTF?!? Her parents were with us the whole time, except for when we were asleep. So how could it have been unsafe? Seriously, the only bad thing was the bathroom situation, lol, but we managed to figure something out.

I've tried talking to her and telling her we weren't in any danger, but she's refusing to budge. I really don't want this to be something that prevents me from ever sleeping over at my friend's place again. So what can I do to convince my mom this really was no big deal?