I can't lunge my horse to save my life; help?

My mare's previous owner, who is also our trainer, lunged her in her bridle and other riding gear without much a problem. I watched him do it once, and she had moved out on about a 40ft circle; he had a very long whip the he held upright while she bucked and ran around. I can deal with bucking and kicking, but I just can't get her to go! I haven't lunged her in about nine weeks, and I used to be able to get her to go out on a twenty foot circle. I tried today to get her to go, and she kept cutting in, even at a walk, and wouldn't move out. She keeps a small 12-ft radius circle and will pin her ears at me and get close to me so she can stop. I keep moving the whip and tugging the rope, but she'll still turn that head in and turn at least one ear at me while flaring her nostrils. Despite my best attempts to move her out, she just keeps making a choppy square kind of shape. When I ask her to trot, she hesitates. She goes into a collected trot and will flip her head and give little squeals if I ask her to go into a working medium trot, and don't get me started on cantering; she bolts, yanks the lunge, and drops to a trot. I know the footing in her paddock is frustrating to work with because it is sand and dirt, and she strains to move in it, but that's the only place smaller than the pasture I can put her in, because I'm nervous about taking her out to the pasture since she dragged me once before during deep heat. She's due to go back into deep heat near July 4th. I don't have an arena to work with; I can work her on 3 acres of my property, two of which are square pastures.