The other answer you have received are very good!
Here are a couple more things to consider:
Put the leash on in the house. Then, just walk away. Be sure to keep an eye on her, because you don't want her running away with it, getting it caught on something. Then, just let her make the next move. Maybe hold up a favorite toy, so she will start to move with it on.
You could also tie a piece of yarn around her neck, no leash, and let her get used to the yarn first.
Dogs can be very "stubborn" sometimes, and their behavior can be altered to cure it.
As a new puppy owner, I highly recommend a video by Ceaser Millan, a Professional Dog Behaviorist. He rehabilitates dogs, and trains people.
He has his own TV program, the Dog Whisperer, on the NGEO (National Geographic) channel, on Friday nights mainly, but also comes on some other days. This video is available from: http://www.dogpsychologycenter.com/
There are other good videos available on the web, but this one is really worth your attention.
Please watch just one of his TV episodes, if you get the channel. You will get "hooked" on it; just like I did. It's GREAT.
I do wish you the best of luck.