story identification - Old SF novel about a white-haired young woman, alien or half-alien, who tutors human kids

I'm trying to remember a science fiction novel I read sometime in the mid-1980s -- I'm sure it was no later than the year 1986.

English language, published in paperback in the USA, with a cover illustration which I think had a white-haired young woman and a couple of human kids standing over on the right-hand side of the picture, seen in profile as they look toward the left. There's plenty of green landscape -- and I think some buildings in a valley below them (i.e. near the center of the cover). I believe I checked this out from a school library, so it may have been aimed at a "juvenile" or "young adult" audience, despite the main viewpoint character being an adult. (On the other hand, I think that same library had plenty of SF/Fantasy books that clearly were not written to appeal to legal minors as the bulk of the target audience.)

I don't think the author was anyone I'd heard of before -- for instance, not Anne McCaffrey or C. J. Cherryh. (I just mention them as examples; I don't recall if the author's name looked masculine or feminine; only that it failed to ring a bell when I found this book on a library shelf.)

I think the title across the top of the front cover was just one weird word which I presumed the author had invented. Possibly the name of an alien race, or an alien/human halfbreed caste, or something along those lines. And I think the title-word began with the letter D. (But I wouldn't swear to that in court.)

Here's what I remember about the characters, plot, and setting:

1. 
   

   The novel took place on Planet Earth, at least a couple of centuries in the future. A spacefaring alien race either ruled the Earth or at least dominated the most civilized portion of it. I have an impression (possibly mistaken!) that there weren't nearly as many big human cities scattered around the globe as there used to be in the 20th Century, but I don't remember if that was because of war with these aliens, or with some other alien race entirely, or a terrible war among the human nations before the aliens ever came along, or what.

   
   



2. 
   

   The start of the novel takes place in the urban area which is the "headquarters" of the high-tech aliens. Near their spaceport, I believe. I have a vague idea that this was stated to be somewhere within the boundaries of the former United States of America.

   
   


3. 
   

   In the opening chapter, as we meet the female character who is the protagonist of the novel, with much or all of the narrative showing us her viewpoint (but in the third person), she is currently tutoring a couple of youngsters who are human kids -- preteen or early teens, I think, one male and one female; and I think they are brother and sister; perhaps the son and daughter of someone very important. (I don't remember if acting as a teacher or tutor was currently the heroine's full-time job, or if she had other duties in her culture.)

   
   


4. 
   

   We quickly learn some interesting things about her. She speaks perfect English (or whatever language the humans of North America are speaking in this future era), but she is either an alien who looks pretty darn humanoid, or else a half-breed whose genes are fifty percent alien and fifty percent human (I simply can't remember which). She is described as having white or silver hair, and also there is something very peculiar about her eyes -- I can't remember what -- which is a dead giveaway regarding alien DNA. However, if she covered or dyed her hair, and covered her eyes with sunglasses, and wore normal clothes, the typical observer might easily believe she was just another human woman.

   
   

Note: I can't recall if there was any hint of any other distinctive physical characteristics which could reveal her as alien, but which would only be noticeable if she exposed most of her skin to a critical human observer -- it didn't matter to the plot; I don't think the situation ever came up. (No scenes set on a beach with the heroine running around in a bikini, for instance.)

5. 
   

   This point about her obviously nonhuman eyes becomes especially important in a tense scene somewhere around the middle of the book. Near I can recall, the heroine, the two human kids, and one human servant (an older man) are traveling on foot in a wilderness area, and they meet someone who is very prejudiced against the aliens. Specifically, when he sees the heroine's hair, and possibly her eyes (I don't recall if she had tinted lenses covering them at this moment), this stranger correctly deduces her alien roots and wants to shoot her on the spot. None of the "good guys" have guns with which to defend themselves. (Since I can't remember what the backstory was regarding how the aliens had come to Earth in the first place, I can't swear that the stranger was being totally unreasonable in regarding those aliens as his enemies.)

   
   


6. 
   

   The human servant tries hard to persuade the guy that the heroine is actually his own beloved daughter, and her hair just happens to be extremely pale . . . but the result is that this servant, rather than the heroine, gets killed. The heroine survives this incident, but I'm having trouble remembering how. (I don't remember her ever coming across as a superb martial artist or any sort of trained killer.) I think they were up in rugged mountain country at the time, so maybe the brave servant and the shooter went over a cliff together, and that was the end of both of 'em? (That feels like it might be right. I have an idea the male servant may have been a trained bodyguard, but I could easily be confusing him with a supporting character from some other book.)

   
   


7. 
   

   Except for the scene I just described, I remember very little about the details of the plot between the opening and closing chapters of the novel. But I believe that when the heroine, the human servant, and the two kids were all running around in the mountains, it wasn't a pleasure outing. It was because they were hiding from someone and/or trying to reach (on foot) a safe place. I think there may have been some sort of attempted coup taking place, or something like that, and this collection of "good guys" had been shot down, or crash-landed, or something, and either didn't have any radio equipment to let them call for help, or else didn't dare broadcast their location under the current circumstances, so they had to spend several days just walking to wherever it was they wanted to go.

   
   
   


8. 
   

   However, I do remember that the final scene of the book is deliberately structured as a reprise of the opening scene. The heroine is talking to the kids again (don't ask me about what), and she gets a summons to go speak to some authority figures (aliens, I'm fairly sure). On the final page, as she is leaving to answer the summons, one of the kids asks her, "Will you be coming back?" (or words to that effect), and the text says she doesn't answer because she doesn't know. That's the end of the novel, and those words used in the final paragraph are precisely how the opening scene ended!

   
   

Does anyone think this sounds familiar? I seem to recall that the author's way with words seemed pretty good to me at the time, even though I didn't fall madly in love with the plot and the characters, and I might like to take a look at other stuff by the same author (or even refresh my memory of this one) if I can pin it down.