leash problem

I went through the exact same thing a few short weeks ago. Our pup was 9 weeks and what I first did was just put a leash on her in the yard, she was having none of it. Took that off and tried again the next day with food bait, didn't really work she still hated it. Went on youtube and watched other people leash train and decided ( I know I am going to get alot of flack for this) to put her on a flexi lead retractable leash I had, its sixteen feet long. Took her in front of my house and just started walking, at around the ten foot mark I think she started getting nervous that I was walking away and with the flexi lead it didnt have that heavy leash feeling to it so she ran and caught up to me. I praised her, gave her a treat and then she ran ahead of me, we only walked about a half block to my mailbox then came back and went back into the yard, I took the leash off her. I repeated the flexi lead the second and third day, she loved it. On the fourth day I put her regular lead back on and used that, this time she did not resist or back up or dig her heals in the grass she actually ran ahead of me, we have done this three times. Next I am going to have to start working on heal because I am not going to be one of those people being dragged by their dog. I think the initial use of the flexi lead was great for leash training but I won't be using that on her again because its just in my opinion not something you want to walk a strong dog on. I found a great leash training video on youtube if you want to check it out, she is using the flexi lead too to leash train and I borrowed that idea from her. How to leash train your Puppy - YouTube

Can you tell us where you got the puppy from?
Who is the breeder?
Did the breeder get the ears cropped?
When were they done?
Are they still on a cup or are they posted?

Do you have a nice breakaway collar on her?
If so, attach a piece of rope to her collar and let it drag on the ground when you are with her and not expecting her to be on leash, this will get her used to something around her neck pulling on it occasionally without blaming you directly.

What do you want the puppy to do? Any particular role or activity?

When you go out in public, given that you are worried about parvo, I would carry her but make sure she gets to meet people and children, and hear and see strange sights. If you need to put her down in public areas, take along a towel or a mat and place her on that and keep her on it.

In Oregon, I would go to Home Depot and put her in a shopping cart and wheel her around (making sure she stays in there). Have your girlfriend help you by pushing the cart while you walk alongside holding her in there but seeing things and hearing and meeting people. Get people to give her small treats (tiny tiny pieces of food) from their hands (assuming they don't have a dog with them).

You HAVE to socialize her. But you have to protect her from parvo until she has had her shots.

You also need to get her enrolled in a puppy kindergarten class to socialize with other puppies - ONCE SHE HAS HAD HER SHOTS SHE SHOULD START CLASSES.