If you ask the horse to go forward and she turns her butt toward you; either you are trying to move her by pushing energy against her head, which would naturally make her move it away from you, leaving her butt facing you.
OR, she is showing you some bad attitude, and that has to be addressed.
If you push her forward by applying energy just behind her shoulder/girth (right where your leg would give the "go" cue) , use your body cues like a slight step toward her raise the hand that is closer to her hindend and "push" her forward with your body energy. YOu have to really MEAN it. Your INTENTION is manifested in how you step toward her and "lift" up your mental energy) If she doesn't move , then you must apply MORE energy, and use the whip. This doesn't mean you have to hit her, but you have to make an impression. Either crack it, or smack the ground or whatever, but you have to get big and mean it. Of course she will bolt forward. Does'nt matter, you asked her to go forward and she did! Now, you try again with a softer ask and more focus on her going forward in a Non-bolt gait. If she still bolts, just keep at it and remember to be as soft as you can but as big as necessary to get a CHANGE. You kind of spiral up in your intensity of asking. Do it like a level One, then a level three and then a level Ten! But always start with a level one low energy and body cues only (no whip). Whip is only for backup if necessary, tho you can keep it THERE, just keep it pointed downward to the sand.
When you start out lunging, don't worry about which gait or the quality of the gait you get. Just get the horse to respect your request to go forward. When you have that, QUIT for the day.
Next day review the "go" stuff and see if you can slow the bolting horse down to a trot and keep it for a bit. Do'nt dull your horse out by running them in endless circles. As you get better at lunging, keep it short and interesting with lots of changes in speed and direction.
As many have said, lunging is an art in itself.