My resident cat is really upset at me...

So I've had my cat, Bijou, for a year. I adopted her as a two year old cat and now she is three. Last year, she lived with two other cats who both belonged to my roommate. At first their introduction was tense, but nothing major happened and Bijou seemed to adjust to them rather quickly and for that year we had no major behavioral problems. Well now that I moved into my new apartment, Bijou became an only cat for about 3-4 months. I felt bad for leaving her alone most of the day and felt like she needed a companion so today I adopted a new kitten to bring home thinking that the introduction would be the same as last time. I know to keep them in a separate room and have kept the new kitten in my bathroom since bringing him home. Well, Bijou has been REALLY upset. Not just at the new kitten, but at me and my roommate as well! She will not let us touch her or get near her without growling or hissing. She is currently hiding under my roommate's bed and refuses to move. I knew aggression is common and to expect it when introducing a new kitten into the home but I did not think that it's normal for her to take out her anger on us! She is normally very sweet and loving and always craves attention but now it's like she's changed to a completely different cat! Is this acceptable behavior for her? Have I scarred her forever??? I love Bijou very much and if it doesn't work out with the new kitten, then I will have to return him to the shelter but I'm afraid of Bijou's drastic personality change. She's never tried to scratch me or bite me before until today. Is it because the kitten's smell is on me? And if so, should I just give her space and time to adjust? It's only been one day but I'm really worried about how this will turn out. 

Cats are very territorial by nature.  When they meet another cat it completely upsets the apple cart.  Cat to cat introductions can take days to weeks to months to many months to work through.  Yet the key is to work on the issues.  Do not just put them together and hope for the best.

I would suggest getting a few Feliway diffuser plug ins.  The phermones will help your cat to feel more calm.  Also give him lots of attention and play time.  Play time is a great way to boost a cats confidence.  You can try the hunt, catch, kill, eat, groom, sleep process.  Get a wand toy or laser pointer and really get him moving.  Aim to play 10 minutes or more.  You want him tired out.  This will satisfy the hunt, catch and kill.  Next offer a small meal or a special treat for the eat.  If he is tired out and he got something yummy to eat, he should groom himself and then take a nap.  You can repeat this 2-3x each day.

Here are some articles and a video on cat to cat introductions.  The key is to take it slowly.  Remember you have a kitten that you do not want injured.  Start today with scent swapping.  Just get 2 clean wash cloths and rub down each cat with one of the cloths.  Next swap the cloths.  Transfer Bijou's scent onto the kitten and the kittens scent onto Bijou.  When you wipe the cats down be sure to get under the chin and the pads of the feet.  THis is where the scent glands are located.  Do the scent swapping for a few days.  You do not want there to be any hissing, growling or other behavior.  Do not move forward until Bijou does not react negatively, but do give it at least a few days before moving forward.  Keep the cats completely separated too.

http://www.thecatsite.com/a/the-ultimate-yet-simplified-guide-to-introducing-cats

http://www.catbehaviorassociates.com/a-simple-little-trick-to-use-during-new-cat-introductions/

http://www.aspca.org/pet-care/virtual-pet-behaviorist/cat-behavior/introducing-your-cat-new-cat

http://jacksongalaxy.com/2010/10/01/cat-to-cat-introductions/

ShadowsRescue has given you some great advice. I don't have a huge amount to add. It sounds like Bijou is just totally thrown by the kitten's arrival. Be sure to keep them totally separate for the time being. Stay patient. Introductions generally take weeks or months, but it's well worth the time and effort.

Bijou isn't mad at any of you - she's just stressed out. Getting some calming and stress busting measures in place would be a good idea. Start with Feliway diffusers, and you may find Spirit Essences and/or Composure helpful too. Also, don't underestimate the power of interactive play. It's a wonderful stress buster, and a great way to increase self and territorial confidence.

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You were already given some excellent advice, but I want to add a personal story because it might make you feel a bit better. My first cat reacted in much the same way as yours when I brought in a second cat. Up until that point I had never heard him hiss or growl, but for a few days after he was distant and would occasionally hiss at me and become upset if I came near him. It was pretty upsetting seeing him go from wanting attention all the time to being stressed out by me. It didn't take long for things to go back to normal though, and now he's just as sweet and loving toward me as he was before I got this second cat. Use some of the tips the others gave you and give your cat some time. You haven't scarred her forever, and I'm sure she'll be just fine in no time!