Cheryl Regena Whitelaw (that should be her full name, check this out!) did do some interesting things with mazes, yeah! In other games she wrote or converted, she used some peculiar pre-made strings that were randomly selected, one for each line of the screen. What came up could be hardly called a maze, but still, they were interesting maps for chasing games!
It's been many months since I last saw the TI-99 listing, but yeah, I still remember that darned FL variable! Yeah, she never allowed FL to have any other value beyond 1, so there was some piece of code that never executed! I made sure of it after I did the "almost 1:1" conversion to XC=BASIC, so that I could add some debug code just to see and understand!
And yes, the whole thing is really messed up; once the Monster starts marking its steps and goes into a dead end, it can't escape... And yeah, the LV variable never increased... MEESSS! :D
Like you said, I tried to catch the original intent, and it seemed to me that she tried to have some "multi-layer" invisible marking of the maze (using the FL variable for that), so that the Monster would try to choose some lesser-walked path first. I tried to do that my way and... it all got messed up as well :)
What I ended up doing (after A LOT of trial and error) was something simple so that the Monster would just mark the whole dead end (while going back on its steps), while all the other passages can be walked on again and again.
Oh, regarding the 180° turns: yep, I remembered this video on Pacman and in particular, the fact that the ghosts never turn around (well, mostly never)! So I really focussed on that, and it paid off!
The Atari version used different graphics for the Player steps according to the direction they went, and I was initially using them. So I could have made the Monster smarter by also reading the direction the Player went, not just the trail per se, but I don't know how much more difficult the game would become.
So, to sum it up: I did what you suggested, I tried to see the original intent and then implementing it my way. It was hard for me, but in the end... it works well enough :)