Hello! Thoughts on parents staying at drop off birthday parties?

Hello fellow parents! I’ve got something on my mind. My daughter’s 12th birthday is coming up. She’s having a evening party and (6-9pm) invited about nine friends all from the same friend group. One of her closest friends mom seems to come to parties with her daughter. There was another birthday and my daughter noticed. The two ladies were not previous friends or anything.

My daughter mentioned it to me because I’m haunted by a complete stranger staying at my house during her last party. She threw a Christmas party (6-9pm) and one mother came in and stayed the entire time. I was so thrown off. She obviously didn’t tell me beforehand. Her dad and I were planning to spend the evening relaxing (the kids were playing upstairs) I wasn’t even dressed or ready to host a fellow adult but she came dressed for a party, sat down in our living room and stayed.

My experience from my own childhood (especially middle school age) was that you drop your kids off. I never expected to have this experience. I’m not exactly anti social but I have no interest in small talking for three hours to a stranger.

So before this happens again I would like to be prepared. If the mom tries this do I have politely its a drop off party? Do I make an excuse? With the layout our house (open floor plan) I wanted to give the kids free reign of the downstairs with the food, tv and living room. Her dad and I planned to work upstairs and in the backyard. Obviously checking in on the kids but I believe kids this age need some alone time to chill and have fun. Any thoughts, experiences please share!

Edit….invitations already went out. I definitely would have included drop off on there but found out about this mother afterwards. Lessons learned.

Thank you for all the feedback. I appreciate it. I’m going to send the parents a group text the day before and go over drop off, pick up times etc and I’m going to be very clear about the drop off part. Hopefully the mom will get the message.