make the kitten being around her a good thing.  give her lots of love and
treats when the little one is around.  Ignore him as much as possible.  Make
sure they have separate corners to go to, separate litter and food areas.  I
would also consider confining him for the day again for a while..

Good luck

In December I brought a Manx (about a year old from the shelter) home to my
4 other cats.  One loved him right away, one couldn't care less, and two
were hissing and angry for a while.  I am happy to say that it all worked
out and now all 5 get along great, although there is the occasional spat
when the young one tries to "play" with the 7-year-old, who has outgrown
that kind of play.

Some hissing, spitting, mean looks are inevitable as they work out their
places in the family.  The real concern is if they ever really get nasty -
biting, really scratching or cat-fighting.  I never let that kind of
behavior be acceptable- they were always temporarily separated if anything
more than reasonable happened.  Be sure to keep them apart when you're not
there until you're sure they will not hurt each other.

I completely agree about spending as much time as possible with your
original cat (your manx) because they really are "person" cats, and mine
gets jealous even when I'm talking to my mice.  Make her feel very special
still.

Good luck!
Meghan