Kate,

Give it some time. They will usually work it out themselves. Give your
older kitty extra attention and spend a lot of time with her.

   You have to understand up front  you can't  throw 2 cats in with one
another this takes time.  You have to separate the cats  let them discover
each other under the door for awhile to figure each other out.  There is
going to be hissing and whining but leave them alone  no punishment this is
natural.

  You can easy the journey  by  taking your clothes that you have worn
today  and rubbing them both with them to give them a same scent so they can
be a little at easy with a known scent.

After a couple days you can let the little one out to explore  with the
other cat put up so no fights will occur   than   in a couple of days you
can let them both out together but under watch  if any biting or fur ripping
happens separate for a few more days.

This takes time and if you do not do it right  there can or will be
territorial issues later on.  There is one thing   some cats will not get
along with other cats no matter what

Make sure you give the older cat some extra love so she still knows she is
loved

By the way  thank you for taking in another kitten

I would put the kitten in a separate room for a week or two -- depending
on how they react to each other. Let them get to know each other under
the door. Put a towel or blanket in the room and then put it out for the
other cat to smell and vice versa.

Give your old cat way more attention than normal. She is going to need a
lot of reassurance.

By the way, don't seclude the new kitten on your bedroom if your old cat
is used to sleeping with you. Keeping the old cat out of a favorite
place and the new one in it could just create more jealousy.

Good luck. This can take time but will be worth it when you see them
snuggling together.

Rhonda

I have gotten the thrill of doing this 2 times in the last year.  It takes
time and patience, and lots of love.  I did lots of reading online about
seperating the cats in the beginning and honestly I never did that, except
for when I was not around them and at night.  And they say that the 2 cats
may never totally get along, but will tolerate each other, Both times I have
done it the cats have become very close.  They play alot, sleep together,
clean each other, they are great!  So just let some time pass, and my cats
had some knock down drag outs.  The vet told me that is totally natural and
the existing cat is just setting her boundaries.  Give lots of love and
patience, and give treats for good behavior!!  It will all work out.