Is she your wife or GF? You mention her as a "she" instead of your wife/gf. I don't agree with this lifestyle, but I suggest you to be there with her, its for her safety. Don't take chances, better be safe than sorry,
Remember, women/wives need to feel they are first place in her husbands's life. Don't leave her alone with anyone, you may end up alone yourself one day, unless you don't care about your relationship, or you care more about yourself than her.
I emphatically endorse your last paragraph.
Six months into my first marriage I blundered horribly and let my young wife go out by herself to an afternoon showing of an Oscar-winning romantic R18 movie with my white and super-spunky best friend who had been my Best Man at our wedding.
At 4 o'clock the following afternoon, fully 24 hours after the movie would have ended, my my wifez---in close company with my slightly shamefaced buddy, arrived back at our home. My buddy remained his car in our driveway while my wife, standing in our kitchen, took less than 10 minutes to explain why she had to leave me, then grabbed a few personal items and clothes and exited the house, re-joined my buddy in his car, and was driven away.
Three days later I received her divorce-lawyer's letter through the letter-slot in the very door my wife had exited through.
At no time prior to the fateful movie-outing did I have the faintest idea that my wife had the hots for my buddy. Some months after my D-Day he confessed All, telling me that he had no prior idea either and that my wife had made her move on him while he was driving her back from the cinema to my home. She got him to pull over outside a conveniently sited motel and confessed her "love" for him, kissed him frantically then went to work on his zipper etc etc. She entered the motel and booked them a room with my buddy following close behind her to conceal the uncontrollable erection she had given him in his car.
I sometimes fondly think that if I had gone with my wife and him to that movie, I would be still married to her and that he would still be my best buddy.
Instead of that, I have had to live with periodically resurging anger and quite some resentment at being so viciously blindsided by my first wife. An arguably mitigating factor was that on the day of her fateful movie-outing with my buddy my wife was slap-bang in the middle of her fertile time and for the three nights before it we had been hard at it trying to make our first baby.
The Moral---if there be one---is
"Never ever let your wife go out alone to an X-rated movie, much less to a soiree where she is surely going to be fucked by a man she could fall in love with. Which is practically any man at all almost anytime coming up to the middle of her cycle".
Results may vary, even if you do keep a secret calender of her reproductive rhythms.