Please help with my dog's jumping/snapping?

We have two six month old lab mixes, Mia & Sadie. We are looking for low cost training for them both right now. Both are super loving dogs. I am having a few problems with them though,namely with Sadie, and I am not sure how to rectify them. It has gotten to the point where I don't feel comfortable with her around the kids, not because she is aggressive but bc she jumps and snaps her jaws. Like she is going for food but missed it? is the way I can describe it. It is very unnerving. She has caught me a few times, and obviously I am taller than the kids. She will jump up and snap her jaws, if that makes sense. I have told her NO (obviously) turned my back on her, etc. but I am not sure what else to do. Please help. I am not sure what else to do.