1- Give her mom exercise and a chance to run! I don't know your exercise schedule, but it sounds like you may be giving too little exercise. My Great Dane would get very erratic on the leash whenever she didn't have good amount of exercise, but after an hour and a half off leash running/playing in a larger SECURE field and (2) 30 minute walks she would happily walk at a nice pace. Up the exercise! She's telling you her amount now isn't enough!
#2- Training. When she pulls, give a quick, sharp tug on the leash and walk in the opposite direction. Praise with treats, vocal, and pets when she is in the zone you want her to be in. She will soon learn pulling will not get her anywhere she wants to go. As well, correct her with a sharp voice command. If this doesn't work and you're strong, stop dead in your tracks AS SOON as she pulls and let her pull while standing in place. Once there's even slight slack, praise her immensely and start walking. Second is very effective in getting the point across IF you stick to it and can really hold her back. Don't give her a correction, just stop, don't speak, don't look at her, don't move, just wait to praise when she does the right thing.
#3- If her pulling is that bad, get a Halts or a no-pull harness to help with training. Treating and praising her when walking along side you will TRAIN her so you don't need it forever. And when she pulls, pull her back around to you and praise once she's back walking next to you.
Good luck!