Guest rules not being followed

I’ve (24f) had a roommate (24f) that I’ve known since college for two years now. When I first moved in we had a conversation about guests. No amount of nights were set but the basic rules of giving a heads up and not letting them stay here alone was verbally agreed upon ( not written unfortunately)

Fast forward to two years into the lease there has now been multiple instances of her bringing people up sometimes at like 3-4am with no notice and they’re just chilling in the common area. I woke up in the middle of the night last night to use the bathroom and went out in my underwear I had to run back to my room and cover up when I heard a random man just chilling in there with no notice.

I’ve already had a conversation with her about this last month and said I would appreciate a heads up so I can control how I present myself when there are guests in the space but now after that it’s happened a handful of times again.

Would it be petty of me to just stop notifying her when my boyfriend is coming over a lot of my frustration comes from the fact that I feel like I’m following an agreement that she feels is optional to her. I understand having a conversation about it would be more mature but I’ve already asked her once I don’t see the productivity in another convo. 

I don’t necessarily care about maintaining an amicable relationship with her but I also don’t want to create unnecessary tensions in a space I have to come home to everyday.