Trying to overcome

My daughter is 7 and she was invited to her first (drop off) classmate birthday party. It’s a “STAY UNDER” not a sleepover where they would stay the night but it’s from 6-9 and they are wearing pajamas, basically everything but actually staying the night. Iv never dropped her off at a strangers house before, I don’t know this kid/ family. But she is so excited, so I told her yes. And although it’s literally only 3 hours this is my nightmare. And I also know she’s getting to age where she will want to do more things alone and I have to learn to be ok but my emotions are Everywhere. I realized my Apple Watch can text my phone so I’m going to have her take that and told her she’s can text me from the watch if for whatever reason she wants to come home early and that’s helping me feel better but man. I’m not ok.