It's only bee four DAYS!   Patience!  Or you could go over an bite the
female's tail real hard and growl at her with the young male watching.
(snicker).

I would start over, using the following, which is a summary of what I saw on
the net, and based on my own recent experience:

The newcomer should be placed in a cage or large pen in a separate room for
about a week. No face-to-face interactions allowed during this first week.

Put the resident cat in a separate room and let the newcomer roam the rest
of the house. The idea is to mix their respective scents and get them used
to their respective scents.

Use separate kitty litters at first.

After a week, let the cats meet face-to-face through the bars of the pen or
having the newcomer in a carrier. There may be a few hisses, but see if that
diminishes and they start chatting with each other.

Continue these introductions through the pen or carrier until there's no
hissing.

With no food in the room, and all doors closed, let the newcomer out of
his/her pen carrier and see whether the cats are friendly. Supervise the
whole time.

After they become friendly, or maybe as they are becoming friendly, set two
dishes of food at opposite ends of the room. Let the two cats eat in the
same room together, from separate dishes. Supervise.

Similar approaches are described at the following:

http://www.fourpaws.org/pages/adopting_pages/introducing_cats.html

http://www.cuhumane.org/topics/catcat.html

http://www.fabcats.org/introducing.html

http://www.thecatsite.com/Cats/Cat_Behavior/Introducing_Cats.html

At least one of the sites said the best match is female/male and
adult/kitten. Good luck! Updates are welcome.

Clip the aggressor's claws. You need to show your resident cat
lots of love and attention. Your resident female might have a
serious anxiety problem. You might be able to tell if she starts
throwing up, or throwing up more than usual. The fact that she is
trying to run away is a bad sign, in my opinion. Cats need to be
able to run away but indoors they cannot. She might be under a
great deal of stress. Do not worry about the feelings of your new
male cat. Play with him and he will be happy.

I think you are lucky that your resident female is not outwardly
violent towards the new male. Is she declawed? if your cats are
declawed, I think that pretty much nukes their welfare.

Last time I had two cats simultaneously, I brought the new guy home to my
established female, and plopped him down in front of her (Su-Lin was 3 1/2
yr old female Siamese, Thai-Lan was 3 month old male Siamese).  Su freaked
and snarled so ... I just grabbed both of them by the scruff of the neck and
rubbed their pusses together, then sat them with both of them in a big chair
with me in the middle.  They glared at each other over my lap for about half
an hour.  Then I let Thai go.  He circled and then got up and sniffed Su
while I held her tight.  That was all the introduction they needed.  Two
days later ... they were playing tag around the house and knocking over
stuff.

I kept the kitten in a separate room and they both got used to each others
smells for five days before I brought the kitten out.  Neither cat is
declawed.

My resident cat is fine otherwise.  She still sleeps with me and get lots of
love.  Still eats and uses her litter box.  She just does not like the
kitten and wants him to leave her alone.

But yeah I thought the fact that she runs from him was not good.  The lady
that was fostering the kitten said that I just need to be patient (really
hard for me) and it might take a month.

Anyone ever had it take that long?

Paige

4 whole days?
You're doomed.  ;)

Give it time. *smiles*

They will in time.

Keep them separate most of the time so that the older one has time to
herself.

When I got Kira many years ago, Fiona hated her. Growled on sight.
Somewhere I have an audio recording of her growling and swearing at
Kira. At about 6 months of age, Kira came down with a bad infection.
Turned out that she had wounds on both ears. A week later, she was
harrassing Fiona, and Fiona bit her on the ear. So, now, years after
losing Fiona, I can look at that notch on Kira's ear and think fondly
of Fiona, leaving her mark.

About a week before Fiona died, I got a photo of them close together on
teh couch. Less than a foot apart. That was the closest I ever saw, but
I was relieved to see that Fiona was accepting her. Shortly after she
died, my mom got her own film developed and showed me the most
wonderful pictures I have ever seen. Fiona and Kira snuggled together.
I cherish those photos.

In Fiona's case, it took about 8 months to get to snuggle time. The
growling quit after only a couple weeks.

Maynard, who didn't care for Kira, but wasn't as offended by her, took
another 4 months or so to decide she was a good buddy. Basically,
losing his best buddy  encouraged him to accept a new buddy. He just
wasn't interested before.

We have another example. Chase is 4 1/2 and still likes to chase Kira
(yes, we named him well). But it usually isn't a problem. And even less
so now that we have a new buddy for him who actually enjoys being
chased.

Give them time. It will most likely work out fine. The older one just
needs to learn it is good to have a friend. And the younger one needs
to learn where the line is.