To various people who posted support for my delimna with Sukey and
RIley fighting (after spotting a strange cat outside): thanks for the
tips, and problem is finally resolved.

I went with the strategy that Phil P. pointed me to (from the maxhouse
website). The idea is to keep the cats separated, but maintain sight,
smell, sound and even touch contact possiblity with a screen. Move food
closer and closer to encourage tolerance of proxemity.

This looked perfect, since isolation behind ordinary doors didn't seem
to be progressing toward any resolution. Also I have a sunroom that the
cats love, and I just needed to move a screen door from the outside
door of this room to the door that communicates with the living room.
Did that a week ago, put Sukey in the room and she promptly slashed her
way through the screen. Leaving the glass door open an inch for
communication, I then found a heavy wire shelf that I had cut to fit in
the door, and that made a barrier she couldn't breech, but she remained
a crazed, howling wreck when put in the room. Her constant howing was
freaking Riley, so I modified the plan: during his lock-up time he was
in the sunroom and the cats had contact, during her lock-up time she
was in the guest room. Don't know why she didn't object to that, but
I'm guessing it didn't seem frustrating. (I also dabbled with various
combinations of Felaway, catnip plant, and anti-anxiety drugs, but
Sukey still freaked).

After two days of seeming calm, I did an experimental meet-and-greet on
Thursday. Sukey had completely forgotten the problem, but Riley was
still off. He watched every move she made and acted a few times like
he'd like to start something, so I gave them two more days of
separation. Yesterday I reintroduced them again. Riley was still a
little different around Sukey - not antagonistic, but he wanted to
sniff her a lot. I let them be, and we've had 24 hours of peace. They
both slept with me last night like normal, and all seems well. The only
alteration I'm maintaining is that I'm giving them each their own food
bowl. They used to take turns, but I don't want them to have any excuse
now for jealousy or irritation with each other. The best thing now is
that the wire barrier, which is actually attractive, can be used in my
study to get ventillation from a forbidden balcony.

So all seems well. I have one more decision to make. In a week I go
away for a 10 day vacation. Do I board the cats in separate rooms at my
vets (plan put in place in middle of battle), or do I have their usual
pet-minder come in and feed (they hide from her, but have the luxury of
being at home together). If they started up another battle, she'd never
know it. I'm leaning towards boarding this time, just in case. Anyone
have insight on this question?