Are you trolling?
You are the plainclothes officer at the other side of the door.
That woman breaks through.
You do what now?
10 seconds later, while you are doing whatever it is that you think should have been done (instead of stopping her), you have another dozen people who have gone through. What happens now?
Oh, by the way, you have congress folk on the the same side of the door as you are and it's your job to protect them.
They are a "group" (loosely speaking) of people radicalized over the last 5 years who had been told by at least 2 people who have the ear of the POTUS that at least one person on the other side of that door needs to be executed by firing squad. Some of them probably have the same mindset as the group who was planning to kidnap the governor of Michigan a while back. They are radicalized people who, in their own incompetent way, thought that they were there to install as president someone who was not elected to the office for the 20th of January. Believing in nonsense can be a dangerous thing (and they do and they are). These are not people on a tour of the grounds.
As it turns out, we now have records of online discussions about bringing restraints and apprehending "traitors". As it turns out, we have photographs of this assault on the Capitol building showing that at least two people were equipped with such restraints (one of them appears have been identified and seems to be ex-military).
They did not take hostages because they did not gain access to the people who they would have targeted as hostages. They did not gain such access because they were stopped, at that doorway, from entering that hallway (as well as, initially, at the front door of the chamber).
But your argument here seems to be that they should have been allowed in because no one knew that they were not good people?