I'm having a real problem with my two cats. I really help someone here
can help. First, some background:

I have two indoor cats: Riley, a neutered male who is 5.5 years old,
and Sukey, a neutered female who is 4.5 years old. I adopted them both
as young kittens, getting Sukey around about Riley's first birthday.
Although Riley was upset at first, it only took him about 10 days to
tolerate Sukey and by 14 days they were fast friends. They played
together, slept together and Riley would groom Sukey, which they both
loved.  Over the years, the overt affection tapered off, but they
continued to be playmates and were very content together - sharing a
food bowl, sharing litterboxes, and never a cross word between them.
That was until 3 days ago.

Tuesday evening the cats were looking out a window and saw a strange
cat outside. This happens from time to time and my cats get very
worked-upe, doing strange meaows and running from window to window to
keep the stranger in sight. I've never worried too much about it,
because I figured it brought a little excitement to their day, and it
only happend a few times a year. Anyway, somehow in this running back
and forth between windows in a heightened mood, Riley and Sukey got in
a scrap with each other. I didn't see it, but it sounded like Sukey
startled Riley and he turned on her. There was hissing and screaming,
and the upshot was that Sukey was really furious at Riley. The whole
rest of the evening she growled and hissed whenever she saw him. He was
freaked out by it and hid under a chair. He was hiding in my study, so
I shut him in with me while I finished my report cards. When I was done
several hours later, Sukey was still upset so I shut her in another
room with what she needed and went to bed. Riley joined me, but was
still very afraid. Every little noise startled him and he staired at
the bedroom entrance like he feared that Sukey was coming (there is no
actual door on my bedroom loft, and he apparently didn't reallize that
she was shut in another room).

In the morning we went down stairs and I let Sukey out. She ran up to
Riley like old times, but he was freaked and hissed. Sukey seemed then
to remember and started growling. Since then it has gotten worse. When
in the same room they hiss and growl at the sight of the other. At
first they kept distance, but then Sukey has started purposely chasing
Riley on sight. I've kept them separated almost exclusively since
Tuesday, so these observations refer to my tests to see where we're at.
If Sukey is shut-up, Riley proceeds as normal in the rest of the house.
If Riley is shut-up, Sukey goes to the room he's in and hisses and
growls. Now I'm keeping them totally separated, each in separate rooms
where they can't get to the other's door. What can I do to get them to
tolerate each other again? I don't need them to be buddies again, but
to just tolerate each other so they can live and eat without fear of
attack. Note, they are not bothered by each others smell, so typical
new cat introduction strategies that rely on getting used to smell are
not relevant here.

Any ideas? I'm a wreck myself in this. Oh - I've called my vet and they
simply recommended separation and Felaway (which I'm using). They said
this is very unusual and never heard of a case this prolonged. I have a
call into a pet behaviour person, but haven't heard back. Thankis for
any help you can give me here.

Becky, Riley and Sukey