Hi Pete,
Congratulations on your new arrival. :D You get to 'restart' her into your household and methods. I take it you're putting her on a diet, eh. Potty little thing.
Don't rule out treats as reward for job well done, if that ends up being the best way to get her attention. Just make them tiny and hard earned. I use the Pupperoni because they easily break into tiny & manageable pieces. If she's dieting, it could be the fastest way to her heart :D
There's also toy reward, but my dogs have absolutely no desire for toys/balls/usual interests. Food [$ praise, that's about it for my limited menu. But they work well, despite my terrier's lack of concentration ]) She too, easily has a little weight problem, but exercise and watching the amount of treats keeps her down.
Here's something that I learned way back when from AKC basic training in the US as a first step prior to the beginning of training --- called Dominance-Down. It's worked on mine and other 'rescued' dogs to kind of relax them and acknowledge who is in charge. This will likely help for her to accept you as leader. If you're talking about dealing with other dogs, that's another tactic..this just deals with humans. No pain, no stress...well, not for long on the stress bit, at least ;-)
Figure out about a half hour of free time on a daily basis. This is at first, as things start to get better, you can ease up to every other day..and so on. Don't schedule it around feedings or walks. You and Lady go into a room away from others. Be relaxed about it. Put tv or music on. Take a book/magazine with you. If you think you need her lead, use it, but make no issue out of it. Have her sit and then lie down.
Don't talk to her other than to give the stay command just one time. Then slowly rest yourself so that you are lying with her neck under your right or left arm. It's easy to lean on her. Whatever works so that you're comfortable and your body is slightly lying over hers, kind of as if she's an armrest. This has to be comfortable to be here for about 15-20 minutes for you. At least, that's your goal to work up to. She might lie quietly for 5 minutes and then decide to get up. Don't let her, but don't say anything. Just pull her back down by the underneath of her collar or where the leash is hooked in.
Lady is there at your convenience, not hers. She could go to sleep. Doubtful at first, but let her, if that's what she chooses. Use the time to read and relax. If she does struggle at first, make her do what you want until she physically relaxes. Then just give her about five minutes to let herself get used to the idea. Then sit up. Work up to the longer time.
Don't let this end on a negative and stressful fight. Thats why you work up to the longer time period. Make it positive for both of you--that's why you adjust her start time for this.
When you end this time alone with her, just sit up, but continue to ignore her. When you leave the room, don't say anything to Lady. Let her think about this new change of status for a bit. If you have any other problems with her not understanding that she is lower than the family members, have everyone do this on a regular basis. Just keep things as calm and low key as you can.
This has basically worked for everyone that I've known who has had problems with their dogs and placement in the pecking order-- all sizes, ages, and genders. (around 40+ in about 6 years since I've known of it). I hope it works for you, also.
good luck & enjoy your new addition :D
toodles