Why is Harris refusing to go to the Border and see for herself the mess they created?

It's called "Plausible Deniability". 

If she doesn't see the problem first hand, she can deny the seriousness and severity of the problem. As long as she never sees the problem, she can continue to claim everything is under control.

Gee I don't know, why don't you just call her up and ask her yourself because no one on this site can give you an answer to this question.

Trump had the border under control, Democrats cannot admit that so they ignore the mess they created.

She's too busy playing golf and fingering porn stars

Oh no wait a minute

edit: Well, it's early. lol

It's not about the problems at the border. Democrats are preparing for a summer of violence in the US again. Only bigger. The Democrats are letting in the insurgents from many other countries to come in to help them against the people. They want you to look at all the other problems at the border because they know it doesn't matter if you know, what are we going to do about it? Just complain. Nothing else. 

Probably afraid of running into one of her ex-johns is my guess.  I've heard that a lot of those detained are sex slave traders who probably know Camel Hairs well.