YOU set the boundaries for YOUR home.
Don't talk her to death - many folks that age hear it the same as the teachers/adults spoke in Charlie Brown (ie wonk wah wonk wa wa wahh wonk wa).
If YOUR boundary, which is about controlling what you will live with - NOT controlling what she's doing when it does not impact you, then it must be respected AND you must be willing to follow through.
Last year, during Covid, I set some pretty harsh (that would have been unreasonable absent a global pandemic) boundaries with my youngest living at home at the time. Before vaccines, when I was BARELY leaving the house other than absolute essentials like groceries 2-3x a month or my MUST do things at work, I was a total hermit. From my perspective, if I wasn't leaving the house, enjoying my own social life, etc in order to keep myself and my family safe, I sure as h*ll wasn't going to live with someone unwilling to make the same sacrifice for MY health. So - no bars, no restaurants, no parties except outdoors, etc. Which sucks for a young adult in their early 20s. Bottom line is my kid didn't abide by it, I learned they were in a place not OK with me, they refused to come home immediately, so they arrived home the next AM to all of their belongings on my front porch. I love my kids, but am not willing to risk my health or my life for them to party. Like LiesHurt - shocked the shit out of my kid. And, like LiesHurt, it was a good thing in the long run - for both of us. Scary AF at times, but my kids know that I mean what I say and I say what I mean. And -I think- they respect it.
The trick is you must be willing to follow through.
dammit - had a whole thing that got deleted - whoops. Your boundary sounds like it's not OK if she's out all night - or out all night w/o telling you. So, that's a boundary and you don't need to explain it or rationalize it or anything. You just say it and say the consequences and then be 1000% prepaared to FOLLOW THROUGH if it's broken. And you don't have to be angry at her about it. It's hard and sad, etc., but it's about you, not her.
FWIW, I don't think it's your beeswax who she's with, where she is, etc. If she was living on campus, you wouldn't know those things, so why does her being at home change that? What DOES impact you is having someone stroll in at 3am or 10 am or whatever when you are worried and don't sleep or get awoken in the middle of the night. Those are things that will impact most folks, whether it's their kid, their friend, or their own parent staying in their home (or it would me, which was part of the deal with my own kid - IOW, I would not invite my 80yo father to my home if he'd been spending time in bars last year - it's about ME and what I want in my home/airspace, not about controlling what you do or do not do and who you do it with).
[This message edited by gmc94 at 6:42 AM, Wednesday, October 20th]