I have multiple times read here that going out to a club with an established GF is a bad idea with the general subtext of her getting to know a better man there. Isn't this extremely blue-pill? It's a lack of confidence. It implies that almost certainly there are better man their meaning your confidence is rather low.

Second point is you can also use such a night out for your own advantage. Just talk to other (at least equal if not better looking) women right there. When she gets a drink and comes back: be talking to a hot chick. When she comes back from the toilet, be talking to a different hot chick. Check out other chicks and don't hide it. And let her imagination do the rest.