It's certainly possible to train her, even if she's already had 4 years of learning that "pulling = moving forward". It might not be as easy as training a younger dog who has less or even no ingrained pulling behaviour, but it's still in the realm of do-able provided there's some commitment and consistency on your part.
kikopup has this playlist on youtube. There should be plenty of tips and exercises in it to give you some ideas and help get you started.
www.youtube.com
kikopup has this playlist on youtube. There should be plenty of tips and exercises in it to give you some ideas and help get you started.

Leash walking Loose Leash PLAYLIST
how to train your dog not to pull no pulling walking on a loose leash leash training dog training clicker training leash walking train your dog to walk by yo...