aiw for skipping school

So, I have a sister named Avery. I'm 18, and she's 16. We share a car a 2010 Jeep Grand Cherokee and we love it to death. By the way, I've already graduated from school, but Avery is still in school.

Since we share the car, I normally drive Avery to school so I can have the car for the rest of the day. Before that, I would just drive her to school and then go about my day.

One day, Avery really didn't want to go to school. I had the whole day off, and I knew I wasn't going to get called in to work. We were sitting in the car while our grandparents were at work. We had already blocked the school's phone number from our grandparents' phones, and we had also blocked the school's emails from both of our grandparents' email accounts. Avery had even made a fake email account pretending to be our grandparents so she could respond to the school while acting like them.

Avery checked and saw that she didn't have any tests that day. So we went out. We went to IHOP for pancakes, then drove around town. We stopped at a bunch of gas stations. After that, we went to McDonald's. I told my grandmother that I was going to have the car for the rest of the day, and she said yes.

We spent the day doing all kinds of things and having a lot of fun. We got home around 8:00 p.m., and our curfew is 9:00 p.m. We got ready for bed and went to sleep. That was the whole day.

Avery said she didn't think anyone would find out that she had skipped school to hang out with me. It was also my day off.

That was two months ago, and our grandmother still doesn't know that Avery skipped school. However, Avery and I filmed TikToks in our car that day. Our grandmother's friend sent her one of the TikToks, and she noticed that the dashboard clock showed 12:00 in the afternoon. I told her I was just having trouble with the radio, but it was actually filmed while we were out that day. Now she's been grilling me with questions. I don't know if she thinks we skipped school, but I'm pretty sure she's onto us.

Also, I know that she has been in our car because it has clearly been looked through. She also took the bumper sticker off the bumper that said "Sisters On board," and she took the $10 that was in my center console. I don't know why she went through our things or why she took those items, but she did.

Now she's been grilling me with questions. I don't know if she thinks we skipped school, but I'm pretty sure she's onto us. So, what do I do?