My cat had an accident - I'm sick with worry!

I live on the third floor of an apartment block and yesterday I didn't
close one of the windows properly. Next thing I realise that I hadn't
seen puss in a while so I went looking for her when I noticed she had
pushed it open and jumped out onto concrete. I ran down and managed to
get her back inside but she had a bloody nose and seemed to be in
shock.

She's a calico, and goes CRAZY when taken to the vet so I thought the
best thing to do was to keep her in her environment and keep her calm.
She was walking around okay & didn't seem to have broken anything
apart from busting her nose.

So she kind of curled up and went into herself so I thought the best
thing to do was to let her be. Then this morning she was still really,
really subdued and I noticed that she was going to the toilet a lot
and passing small amounts of blood. I also read lots on the internet
last night about cats dying from going into shock so I got her into
the vets at 11 am this morning. (she had her fall about 2pm yesterday)
As expected the vets examination was traumatic for the cat she ended
up biting the vet and on one of his shelves. But we got her down & he
gave her anti-shock meds & painkillers. He said that she had injured
her back but couldn't tell how severe the damage was without doing x-
rays. So he's keeping her in today & tomorrow.

I feel so guilty! I should have made sure the close the window
properly and brought her to the vet IMMEDIATELY after it happened.
She's up there now and I know she is going to be totally stressed out
& I am convinced she is going to die in a cage up there from some
internal injury. It's Sunday today so there is probably no supervision
up there today/tonight.

The vet said there was no threat to her life and that I shouldn't
worry but I just KNOW the cat isn't going to get better. And if there
is a chance she'll probably require surgery in another district so I
don't know if it would be better to let her go!

Has anyone had similar experiences with back injuries and cats? She
seemed okay yesterday but for being subdued & was even purring this
morning & was walking okay and everything.

I should mention that this is my brothers cat who passed away a couple
of years ago. He ADORED her so she has to be make it. I've been crying
all day thinking about him and the cat being frightened up in the
vets. What am I going to do??