A couple things.
First, did she swipe your hands twice with the little circle thing? Or did she do your hands then something else? If she did your hands the only reason it'd be done twice is if for some reason the swipe they did was not done correctly to get a decent reading off the machine.
Second, was there X-ray machines as you were going through (Gotta imagine there was unless it was a tiny flight). In general what you're saying with undoing your whole bag like that would be unusual I believe...then again, I did not do checkpoint and their x-rays worked different than baggage so admittedly there may be other policies there. It seems weird that she'd go through all your stuff but it may due to two reasons. Which takes me to...
Third, "Secondary" means secondary screening. This is screening that is beyond the standard procedures of running you through the metal detector (and sniffer if they have one) and having your stuff go through the x-ray. If they have to have you walk over and get a more thurough inspection that is called "secondary screening". This happens when people have issues that require it, such as medical devices or issues when someone has significant metal in their body. It also happens at random intervals as well I believe. There are strict protocols on what to do with regards to this and everything is supposed to be articulated to the passenger and asked of them prior to acting.
Fourth, this all leads me to a conclussion about Carla. Carla was probably a rather new person into the field and one that didn't, sadly, listen to closely during training. The lack of knowing what a secondary means helps lead me to believe this. The rather disorganized way you seem to suggest she acted with your bag also sounds like someone whose relatively new and hasn't fully had their supervisors come down on them yet for the poor workmanship. Its also why it likely took you far longer than it should've. Secondary screening is more time intensive but even then if everything is going smoothly it shouldn't be more than 10 or so minutes at the upper end as the purpose is primarily to get people moving and get them to their flights saftely.
If this was at a major airport this all makes even more sense to me as to the reasons it happens. While yes, I understand and would agree part of it is arguably overbearing TSA policy, another part of it is the sad state of things with the agency. Many in the public dislike the notion of TSA as a whole and having to deal with it, many of which don't just attribute the heightened saftey procedures to them but even forget that much of what they do was already done by private companies prior to it anyways. The various regulations passed by higher up that people dislike end up being vented at the employees on the line as they are the face of TSA for so many people. The pay, especially in places like DC, is attrociously low and promotion potential is very small. Due to this turnover is high which means you're always likely on any trip to have a decent chance of likely running into, either directly or as your bag travels, someone who is 4 months or less on the job.
Which I think is where most of the issue comes in when you get complaints that aren't about attitude but about actions. The training is uniformed across all the agency, and its good training. But you're advertising a position that could use intelligent people to fill it, but only requires a high school diploma and only pays like a job that you'd get with only a high school diploma. So you have continually new people, some of which who may not have cared all that much about paying attention or grasping the training, and when that happens procedures sometimes get messed up...sometimes erring on the side of overzealous in hopes of not getting in trouble for not doing enough. I'm not saying that's right, its not, but I think that's where most of these cases come in more than people trying to "abuse power" or purposefully "incompotent".
The public simply wants the impossible, as is so often with people. They want skilled, intelligent, professional people who know what they're doing...and they hate that there's so many of them and demand that the agency doesn't spend a ton of money while having many people take their TSA general frustrations out on the ground level people. The two desires don't mix well.
