I don't know how old your pup is, but both my dogs went through a stage of non-stop peeing when they were pups. One is still a pup and is in the midst of that stage now.
I got a belly band for him to help keep it off of the floor and it seems to help him not tee in the house too. I don't think he likes to tee in the thing so it's deterring him a bit. At the moment it is MIA and I wish I could find it! They come in the female version too. It's sort of a diaper for when they're in heat so males can't get through, but it works the same for pottying. Like I said though, I use it just to keep it off of the floor, not to let him use in place of going out. Although, it is less stressful if he gets away out of sight for a moment.
I'm also tethering and that helps. Helps me keep an eye on him, helps keep him from teeing where he shouldn't...
I know what you mean though; you try to watch them and catch it before it happens, and I bet you're already taking her out quite often enough. At this stage, you can take them out, they'll tee, and turn right around 15 minutes later and tee on the floor. Who would have seen that coming??
I think it's a stage they go through and it passes. It did with my other one and he's pretty reliable now.
I would get the enzyme cleaner. It will help! It's not 100%, none of them on the market are; but they really help. I use Out!. The problem is that once they use a certain spot so many times, it doesn't matter what it smells like. They're most likely using it for the same reason they did the first time when it had no smell - it looks like a good place to go. But the Out! will help keep the odor out of your home.