When I say new relationship its been less than 6 months. I can say I care about her a great deal. She is a wonderful person and helped me through a lot in that short amount of time.
Let me clarify my question now. I am not going anywhere, I am not thinking of leaving her or anything. What I mean is this. Since she has found out she has cancer she has done a complete 180. She's is not the same person I started to fall for. We would spend hours upon hours talking when we are not together. Now she's cranky most of the time, my feelings don't matter at all, she seems like she would rather talk to her male best friend than me. Also, a point of contention is my brother. They do not like each other and he does not think she is good for me but he is a whole different story in itself. I am just not sure what to do when interacting with her. I told her that I am not going anywhere I will be by her side no matter what happens. I feel like she is pushing me away.
I work nights but luckily for me I am in the IT field and can basically do whatever I want as long as nothing big happens and my job is done. She was supposed to call me tonight instead she calls her male best friend and talks to him for hours and then calls me and says "I am going to bed. Good night! Can we talk in the morning?" She knows at that time of morning I can't talk because I am wrapping up things at work. I don't know maybe I am being a bit selfish here or petty but with the hours I work and not having weekends off she is the 1 thing I look forward to. I have totally adjusted my work and life schedule for her. I made it so I don't have weekends off anymore to have my days off during the week. I sleep a broken schedule to make sure I am around for her. I hardly spend time with anyone but her until recently. Not really sure what to do here. Let me reiterate I do care about her very much and seen a future with her before all this happened. I still want to be able to see a future with her. I wouldn't care if she was told she only had 6 months to live. I would love her and try to give her the best 6 months possible. Just not really sure to handle and deal with her mood swings. I feel like I have to walk on eggshells with her constantly. She also tells me she wants me to talk to her about my stress but when I do she gets mad at me telling me I am stressing her out. How do I win?

Well,
Thw first thing you have to realize is she is going through denial and anger, and all of the other emotions that occur when one is diagnosed with cancer.
Just be there for her, as you have said you care about her.
Find out through research more about the type of cancer she has, the cure rate, etc. Just knowing the facts is very important.
Even though you don't feel as if you can win, you just being there even when she acts like she doesn't want you there is key.
She may try to push you away because your relationship is pretty new, and she may feel that she hasn't known you that long to share all of these things she is sharing with her best friend. Women are very different then men. They think differently and act differently.
She is doing what she feels she needs to to gain support through all of this.
Hang in there and let her know you care. Do small things like sending caring notes and small token of love like stuffed animals, flowers, etc.
If you really do care, now is the time to let her know it.

I bet her friend is a good listener, and doesn't take her mood swings personally.

That's about the way you have to be also as she is probably afraid and in need of support. You can do that quietly, and letting her vent, but never ever show your stress or irritation, as in fact your best has to always be upfront when with her, either over the phone, or in person.

Lose the attitude about what your going through, and give your best, whether its appreciated, or not, and there is no room for jealousy.

Be nice if you, and the friend could get along, for the common goal of support, for someone you both care about.

Sorry to say,it just can't be about you right now.She is too wrapped up in her own problems.

You should educate yourself about her specific cancer and offer to go to the doctor with her or discuss with her what treatment plans she is going to have and how you can help her through this.

You also need a good support network,but it can't be her right now.

Cancer is not the death sentence it was even 10 years ago so know that recovery is very possible.I am a 29 yr.survivor ,so I know it happens.

Arm yourself with knowledge about her cancer and also on how to support a cancer patient.

People lose their identity to cancer and begin to feel like a cancer patient first and a person second.

It is important to understand the psychological implication of the disease.Arm yourself with knowledge and you will be better prepared to understand her mental state.
Best of luck.

First and foremost, you need to take care of yourself emotionally. You are in a new relationship and now is not the time to lose your identity. Your girlfriend seems to be struggling with her new identity as having cancer. It might be that her male best friend provides her with the identity that she desperately wants back. Maybe she needs to reflect on happy times to help her through her illness, and you can't do that. You can only provide her with love and support if she wants to look forward and not backwards. Give her some time and I'm sure she'll embrace the time she has with you.