I’m interested to see that co-ed sleepovers are happening in the US! I have only raised my kids abroad (and they were NOT a think when I was growing up in the US.) I had assumed it was a European thing because all the French/Dutch/Norwegian kids my daughter knows seem to think they are a normal thing. I am generally a fairly liberal parent - but before I was even asked I made it clear that co-ed sleepovers would not be happening.
I do let my 16 year old go to parties and bars. Situation here is different - kids have drivers who wait around for them and bring them home. I don’t expect her to be drinking at this age and she knows the freedom she enjoys now can just as easily disappear.
I would not allow her to attend a party at a “farmhouse” - code for unsupervised party in a remote location.