Are you the only person training your dog?
1. Get a well fitted collar. You want tight enough so that you can only put two fingers between it and her neck. If she is still growing, check it frequently.
2. Consider using her food to train her. If she eats 2 cups of food a day in two seperate meals, divide it into smaller potions and have her sit before giving her each portion. EX. Give her 1/4 cup food after she sits. When she finishes eating that, tell her to sit again. When she does that give her another 1/4 cup. Repeat until her normal serving is done. If she eats 1 cup of food per meal, that will be 4 sits you got out of her.
3. Use every opportunity you have to train her. If you are going to give her a treat or bone, make her sit and wait. If you are giving her fresh water and she's thirsty, have her down and wait. If she gets up, do NOT give her the food and wait until she complies. She has to EARN everything.
4. I like using head collars on dogs that pull during walks. I feel that it gives me more control over the dog.
If you have Animal Planet, you need to watch the show "It's Me Or The Dog". Better yet, submit your family and dog for the show. Victoria Stilwell does wonderful training that uses minimal force from the owner.