I do not feel exactly the same way Coulter does, but I do largely agree with her that much of what he is doing will be useless if he does not build the border wall.
So, in the interest of understanding where Coulter, and people like her are coming from, here is some of what she has said in recent days.
I, and other Trump supporters, ALWAYS knew he was a coarse vulgarian. It's in "In Trump We Trust!" That's why we trusted him.— Ann Coulter (@AnnCoulter) March 28, 2018
ITWT: "The problem with trying to find an old-school WASPy, under-stated, dry, less-is-more, antique leather, sturdy wood-and-brass type to take Trump’s positions is that all those people agree with NPR on everything. Their good taste is their undoing."— Ann Coulter (@AnnCoulter) March 28, 2018
ITWT: "Only someone who brags about his airline’s seatbelt buckles being made of solid gold would have the balls to do what Trump is doing. Being crude is an indispensable requirement."— Ann Coulter (@AnnCoulter) March 28, 2018
ITWT: "The standard riposte to someone who wants to restrict immigration is: You don’t understand—your positions are very gauche, very déclassé. They’re not shared by the people you want to impress. These are the opinions of ethnics in the outer boroughs."— Ann Coulter (@AnnCoulter) March 28, 2018
And that is what is important.ITWT: "Other people would say, 'Oh, my gosh—did anyone see?' Trump said, Yeah, I think I still want to build a wall."— Ann Coulter (@AnnCoulter) March 28, 2018
She is not being "disloyal". She is telling him, "Hey, do what you promised."
If anything, he is being disloyal to the people who elected him.