Depression is an illness and should be treated by a psychiatrist and therapist along with possible meds. You should encourage her to get help.

I have tried but she refuses to take meds or go to a doctor and I am at a loss because I am the bad guy and am told I need to fix it and learn hoe to deal with her. I have to be the one to change not her trying to get help or take the help I have offered

The only thing you can do is support her by listening and being there for her. You can't fix her. She will have to decide on her own that she wants to get better.

As a woman struggling with depression who has a supportive boyfriend, I can give some tips on how he has helped me. When I stopped taking my medication he was firm with his suggestions but they came from a place of caring and he didn't scold or judge me. And I really appreciated that. He also asks me about my self care needs like have I eaten that day, do I need a shower, etc. he will offer to help me get those things done by getting food for me or actually even showering with me. Sometimes he asks me to go for a walk with him because he knows I just need a change of scenery and that exercise is good for the mind too. Those are the little things that make a huge difference that someone who isn't a mental health professional but a member of someone's support group can do. And I say support group with meaning. You can't do this alone. She will need to want help and get more help from a professional to get better. All you can do is support her. I hope some of my ideas help. You're brave just for reaching out to help her. I know I would feel so loved if someone did that for me. (They may have and I just don't know it)

Bagofhopes, I agree with your post.

It's difficult when the person doesn't want the help. It's like fighting with the wind, it's pointless. Sometimes, just being the silent presence for them makes the world of a difference.

I wonder why you're worried about losing her? Is she trying to break up with you? Are you afraid she's slipping into a dark place, is that what you mean when you say you're worried about losing her? Or are you afraid you'll have to leave her because you feel like you can't help her?
She is refusing help, right? And yet you think you need to fix this and learn how to deal with it? You can't fix this. I suppose you could learn to be unhappy along with her, but it won't fix anything. Sorry to sound like such a downer, but if it helps I'm your girlfriend and my husband is you. There is one big difference, I don't refuse help, well sometimes I do, and I am on meds. It's hard for me to admit, but at times I want to blame my husband.
I wish I had the advice that you're seeking. Dealing with a depressed mess of a girlfriend isn't a walk in the park, ask my husband. You're a good man to be looking for answers.
I can tell you what not to say, if that's helpful. Maybe I'm just speaking for myself here. Anyway, don't say things like "get over it", I know I would if I could. In the past, a long time ago, my husband would say "can't you even try to act normal?", I especially disliked that one! And believe me, I took it to heart and tried to act normal! Not a good idea! We laugh about that one now!
Be honest with her. Good advice in any situation, eh?

I don't believe her, to be honest. I think she's got a racket going.

So I would call her bluff. If she genuinely has a problem and she's over the age of 18 she can be a grown up, and deal with the problem. It's not your job - it's her job. She's a big girl now, you're not her daddy.

So if she won't see a doctor, I would stand there and tell her it was clear to me she had no problem, because anybody with a problem and half a brain would then proceed to solve the problem.

Wouldn't they.

Let's stop the clock here, and ask why you're afraid to lose her. What is it about you that makes you feel you can't do that? What makes you feel you can't find another girlfriend?

What are your expectations on how YOU are treated? Do you matter? Do your feelings matter? How important are you?

Do you feel you get your fair share out of this relationship, or do you feel tossed around on stormy seas, always trying but never quite managing to do whatever the firetruck it is she wants from you today?

And do you find that exciting, or exhausting? Can you get anything else done besides be her lackey?

Just imagine her as the mother of your children. Just sit down and do that for a minute.

There are a few things in your post that concern me. It should NEVER be your job to fix her; NOBODY has that job except for her. Mental illness is a hard thing, and the most important part is that the person with the illness needs to step up and take responsibility for recovery. You can be a cheer leader for her, you can help motivate her, but she must take the lead sooner or later. If she never takes the lead, she will never recover.

As for meds, it is my belief that meds only really work if the depression comes from a brain chemical balance problem, or if there is some sort of brain damage. For example, if her depression comes from physical abuse that she received, then coming to terms with that abuse is crucial. Meds may help calm her, but the abuse is the key. OTOH, if her depression comes from some body chemistry issue, counseling may help her recognize the problem and correct it, but that inbalance will always be there.

(As a note, there is research that suggests that risk taking behavior is related to how the brain deals with dopamine:

http://content.time.com/time/health/article/0,8599,1869106,00.html

It is my untrained belief that if there is a link like this between a chemical and risk taking beahvior, there are many other chemical-behaviors that we do not understand at this time. Hence my belief that there are some forms of behavior that require medication to address.)

There is a phrase that therapists use, "danger to themself or others". It sounds like your girlfriend is a danger to herself, but she does not recognize or accept it yet. You can't force her to accept this, so in a way she is right. You can only change yourself, and you need to see if you are willing to accept her for what she is at this point in time. If not, can you be part of a support network that encourages her to change. The latter is a hard one, she may not be willing to accept that she needs to change, and she may push away many people from her life before she does accept that.

Gentle hugs, you are in a hard spot.

I think it's very sweet of you to be seeking help like this but I agree with ThePepperMan, it should NEVER be your job to fix her. Compensating for her lack of engagement (which should never be your responsibility) is enormously different from being supportive.
Depression can be incapacitating but don't be fooled into thinking that it prevents people from recognizing their innate responsibility to deal with it (if they do think they are somehow removed from that responsibility, it's because of who they are as a person/their personality, not because of their depression, and should be dealt with separately).

Otherwise, the advise bagofnopes gave I think is perfect.

There is a group here at DS for depression supporters that might be helpful.