Okay, so entirely by coincidence (no, really!) I came across another appearance of this woman, in
Laura. She was the woman driving the jeep, who Magnum videotaped as he and Rick were driving down the road. Screenshot below:
No wait, whoa. My mistake, that isn't her at all.
Here she is:
I see everything now. These scenes were weaved into the series in order to create a backstory for an epic two part episode, one that subsequently became a "lost" episode. In the lost episode this woman was a stalker, who over the course of years developed an unhealthy obsession with Magnum. She set up these situations where she would "accidentally" run into Magnum, in order to eventually gain his affection. Yes, everyone could see that she was beautiful on the outside, but what people couldn't see is that on the inside she was driving down a one way street to criminal insanity. When she realized she would never capture Magnum's heart, she turned to more obvious ways of attracting his attention, à la
The Ripper in Death and Taxes. The episode was to be titled Hell Hath No Fury.
Surely since three episodes in which she appeared were found so quickly, she was likely in other episodes as well? All I know is the show's creators were very clever in the way they planned so far ahead for her future episode. Shame it was never made.