Women are great at reading men. They are able to instinctively pick up how invested a man is or where they stand with him. They seem to know how much to give and when to pull back. This is because for many, many years, emotionally manipulating men was absolutely essential for their survival. They didn't possess the brute strength of the male to protect and provide for themselves, their survival depended on their ability to sway and manipulate men to fulfill their needs and wants. The better they were at understanding men, the better their chances of surviving.
Men on the other hand, tend to be terrible at reading women. They didn't need to manipulate or sway women for their survival, they could generally survive on their own simply by co operating with the other men. This means that men tend to be far worse at knowing where they stand with their women and they often don't know how much to give. More often than not they're completely blindsided when their encounters with women blow up and fall apart. For women it's intrinsic, for men, it's a skill that needs to be learned and harnessed.
The first step most take as an early Red Piller is defense mechanisms. Learning to recognize potentially harmful behaviors and react. Like if she want's to go with her slutty friends to Europe for the summer you inform her that that will be the end of your relationship. This is a useful tool to learn, it helps you avoid situations where you later find out she was blowing Chad and his buddies in his lowered Nissan Skyline, but it's not where it ends. Defense mechanisms are simply treating the symptoms, they are not designed to treat the disease.
If your woman is talking to you about going to Europe with her friends, the problem is not going to Europe, the problem is that she even wants to go to Europe. It's indicative that "girls party time" is more important to her than the sanctity of her relationship. Women who are smitten with their men don't want to go to on trips with their hoe friends, they don't want to go on coffee dates with "hes just a guy friend", they avoid those situations all on their own because they don't want to risk losing the what they've got.
You telling her that you'll end it if she goes doesn't mean that she didn't want to go and a similar problem will manifest in a different way soon after. This is because you're not in control, you're doing damage control. You're not dictating the frame, you're reacting to it. Had you been more in tune with her behavior and better at reading it, you would have noticed the signs long before. You would have reacted and she would never get to the point where she's coming to you with ridiculous requests.
How do you know? What do you look for?
First you need to establish a baseline dynamic between you two. It can be whatever you want, but male-female relationships function best with masculine dominance and feminine submission. I like mine where she's sweet and submissive. She messages first, she does cute little things for me, cleans my place, fucks me like an animal and doesn't go out to places she knows could be compromising. She cock blocks other dudes herself and always respects me, no bitchiness allowed. That is my baseline, it's how things always are. From there on out it's simply maintaining that baseline with a healthy amount of subtle dread, like keeping up my appearance, my career, social life and generally not falling into beta bitch habits(If you are unaware of how to establish a dominant baseline, you should only be focusing on gaining experience).
The signs that tell me that things are veering off path is when there are deviations from that baseline. A women's behavior is a projection of her internal state, if her behavior is changing, it's early signs that her feelings are changing. If you notice she's not messaging as much, or she's being less sweet, she's being more bold and bitchy or the biggest most obvious tell-tale sign with women, when shes not as keen sexually, then it's an alarm bell and you need to take back control. It's a clear sign that she is getting too comfortable and comfort kills attraction.
The simple fix is to change gears from subtle dread to direct dread. Withdraw attention from her, communicate less, be less affectionate, talk to other girls directly. Due to women's heightened ability to read male behavior she'll quickly pick up that her behavior is yielding a negative response from you, pushing you away and reducing your interest. This will spark tension and competition anxiety as the prospect of losing you dawns on her. She'll then adjust her behavior back to what works and you'll be back at your baseline. Continue this for as long as you want the relationship to last. Notice the changes, react, back to baseline.
This allows you to consistently dictate the frame of the relationship. It allows you to establish the baseline you desire and maintain it. You're not allowing small symptoms to fester into monumental shit test like hoe trips with the girls or coffee dates with Barry. You're being proactive and nipping it in the bud to give your self the interactions with women you desire. When guys go on askTRP saying their women is acting up what they're really saying is they've missed all the signs that there's was a problem and its finally manifested into a shitfest.